So, I am a rather new pfSense kid on the block, however that has not stopped me from changing out software/hardware whenever possible to get pfSense out there!
That being said, while shopping on eBay the other day for another Firebox, I stumbled upon a different security appliance that I thought would make a great addition at work. So without further adieu, the addition of the Symantec Security Gateway 5420 can be added to the security appliance installed list with success! (at least for me!

)
So notes on the installation for anyone thinking of trying this in the future:
1) Disable ACPI upon/during/after installation -- seems the HD controller on the IWill board does not enjoy it much.
2) Remove the SSD drive as well as unplug / remove the original HD that came with the appliance (just in case stuff doesn't work

)
3) Unplug the COM port cable that is located near the external com port connector -- this seems to drive the external display in which trying to run a console can be a bit confusing at times

Otherwise --- here is a screenie or two -- as well as a dmesg:
(pictures are from Matias Soler which gave me the idea that it could be done, his blog can be read here:
http://gnuler.blogspot.com/)

dmesg report:Copyright (c) 1992-2008 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 7.0-RELEASE-p8 #0: Thu Jan 8 22:14:43 EST 2009
sullrich@freebsd7-releng_1_2_1.pfsense.org:/usr/obj.pfSense/usr/src/sys/pfSense_wrap.7
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Celeron(R) CPU 2.00GHz (1992.62-MHz 686-class CPU)
Origin = "GenuineIntel" Id = 0xf29 Stepping = 9
Features=0xbfebf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
Features2=0x4400<CNXT-ID,xTPR>
real memory = 528416768 (503 MB)
avail memory = 507404288 (483 MB)
wlan: mac acl policy registered
ath_hal: 0.9.20.3 (AR5210, AR5211, AR5212, RF5111, RF5112, RF2413, RF5413)
cryptosoft0: <software crypto> on motherboard
cpu0 on motherboard
pcib0: <Host to PCI bridge> pcibus 0 on motherboard
pir0: <PCI Interrupt Routing Table: 14 Entries> on motherboard
pci0: <PCI bus> on pcib0
vgapci0: <VGA-compatible display> mem 0xc0000000-0xc7ffffff,0xe0200000-0xe027ffff irq 11 at device 2.0 on pci0
uhci0: <Intel 82801DB (ICH4) USB controller USB-A> port 0xe000-0xe01f irq 11 at device 29.0 on pci0
uhci0: [GIANT-LOCKED]
uhci0: [ITHREAD]
usb0: <Intel 82801DB (ICH4) USB controller USB-A> on uhci0
usb0: USB revision 1.0
uhub0: <Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb0
uhub0: 2 ports with 2 removable, self powered
uhci1: <Intel 82801DB (ICH4) USB controller USB-B> port 0xe020-0xe03f irq 10 at device 29.1 on pci0
uhci1: [GIANT-LOCKED]
uhci1: [ITHREAD]
usb1: <Intel 82801DB (ICH4) USB controller USB-B> on uhci1
usb1: USB revision 1.0
uhub1: <Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb1
uhub1: 2 ports with 2 removable, self powered
uhci2: <Intel 82801DB (ICH4) USB controller USB-C> port 0xe040-0xe05f irq 9 at device 29.2 on pci0
uhci2: [GIANT-LOCKED]
uhci2: [ITHREAD]
usb2: <Intel 82801DB (ICH4) USB controller USB-C> on uhci2
usb2: USB revision 1.0
uhub2: <Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb2
uhub2: 2 ports with 2 removable, self powered
ehci0: <Intel 82801DB/L/M (ICH4) USB 2.0 controller> mem 0xe0280000-0xe02803ff irq 5 at device 29.7 on pci0
ehci0: [GIANT-LOCKED]
ehci0: [ITHREAD]
usb3: EHCI version 1.0
usb3: companion controllers, 2 ports each: usb0 usb1 usb2
usb3: <Intel 82801DB/L/M (ICH4) USB 2.0 controller> on ehci0
usb3: USB revision 2.0
uhub3: <Intel EHCI root hub, class 9/0, rev 2.00/1.00, addr 1> on usb3
uhub3: 6 ports with 6 removable, self powered
pcib1: <PCIBIOS PCI-PCI bridge> at device 30.0 on pci0
pci1: <PCI bus> on pcib1
fxp0: <Intel 82551 Pro/100 Ethernet> port 0xd000-0xd03f mem 0xe0000000-0xe0000fff,0xe0020000-0xe003ffff irq 11 at device 0.0 on pci1
miibus0: <MII bus> on fxp0
inphy0: <i82555 10/100 media interface> PHY 1 on miibus0
inphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp0: Ethernet address: 00:d0:68:02:e7:93
fxp0: [ITHREAD]
fxp1: <Intel 82551 Pro/100 Ethernet> port 0xd040-0xd07f mem 0xe0001000-0xe0001fff,0xe0040000-0xe005ffff irq 7 at device 1.0 on pci1
miibus1: <MII bus> on fxp1
inphy1: <i82555 10/100 media interface> PHY 1 on miibus1
inphy1: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp1: Ethernet address: 00:d0:68:02:e7:94
fxp1: [ITHREAD]
fxp2: <Intel 82551 Pro/100 Ethernet> port 0xd080-0xd0bf mem 0xe0002000-0xe0002fff,0xe0060000-0xe007ffff irq 9 at device 2.0 on pci1
miibus2: <MII bus> on fxp2
inphy2: <i82555 10/100 media interface> PHY 1 on miibus2
inphy2: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp2: Ethernet address: 00:d0:68:02:e7:95
fxp2: [ITHREAD]
fxp3: <Intel 82551 Pro/100 Ethernet> port 0xd0c0-0xd0ff mem 0xe0003000-0xe0003fff,0xe0080000-0xe009ffff irq 10 at device 3.0 on pci1
miibus3: <MII bus> on fxp3
inphy3: <i82555 10/100 media interface> PHY 1 on miibus3
inphy3: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp3: Ethernet address: 00:d0:68:02:e7:96
fxp3: [ITHREAD]
fxp4: <Intel 82551 Pro/100 Ethernet> port 0xd100-0xd13f mem 0xe0004000-0xe0004fff,0xe00a0000-0xe00bffff irq 11 at device 4.0 on pci1
miibus4: <MII bus> on fxp4
inphy4: <i82555 10/100 media interface> PHY 1 on miibus4
inphy4: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp4: Ethernet address: 00:d0:68:02:e7:97
fxp4: [ITHREAD]
fxp5: <Intel 82551 Pro/100 Ethernet> port 0xd140-0xd17f mem 0xe0005000-0xe0005fff,0xe00c0000-0xe00dffff irq 10 at device 5.0 on pci1
miibus5: <MII bus> on fxp5
inphy5: <i82555 10/100 media interface> PHY 1 on miibus5
inphy5: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp5: Ethernet address: 00:d0:68:02:e7:98
fxp5: [ITHREAD]
ubsec0 mem 0xe0010000-0xe001ffff irq 9 at device 6.0 on pci1
ubsec0: [ITHREAD]
ubsec0: Broadcom 5823
isab0: <PCI-ISA bridge> at device 31.0 on pci0
isa0: <ISA bus> on isab0
atapci0: <Intel ICH4 UDMA100 controller> port 0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0xe060-0xe06f mem 0xe0280400-0xe02807ff at device 31.1 on pci0
ata0: <ATA channel 0> on atapci0
ata0: [ITHREAD]
ata1: <ATA channel 1> on atapci0
ata1: [ITHREAD]
pci0: <serial bus, SMBus> at device 31.3 (no driver attached)
pnpbios: error 1 making BIOS16 call
orm0: <ISA Option ROMs> at iomem 0xc0000-0xcafff,0xe0000-0xeffff pnpid ORM0000 on isa0
ppc0: parallel port not found.
sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0
sio0: type 16550A, console
sio0: [FILTER]
sio1 at port 0x2f8-0x2ff irq 3 on isa0
sio1: type 16550A
sio1: [FILTER]
speaker0: <PC speaker> at port 0x61 pnpid PNP0800 on isa0
unknown: <PNP0c01> can't assign resources (memory)
unknown: <PNP0501> can't assign resources (port)
Timecounter "TSC" frequency 1992624860 Hz quality 800
Timecounters tick every 10.000 msec
Fast IPsec: Initialized Security Association Processing.
ad0: 38166MB <WDC WD400JB-00FMA0 13.03G13> at ata0-master UDMA100
Hope this helps
Dayblade