It probably won't be sufficient for 60Mbps.
I can get ~50Mbps VPN throughput from my 1.5GHz Pentium-M box which is of similar processing power.
That's best I managed after trying various encryption types. It would be a lot less if you require a greater level of encryption. That was using a single connection, the extra overhead from several connections may also reduce throughput.
Some more detailed Atom test results were posted by databeestje here
. Though that is for a dual core Atom.