I am not aware of any but drawing on my own experience, I would say that if you buy a router that meets your requirements while handling Unencrypted traffic, then the same will work well with encryption, provided you are selective about the traffic you move through the tunnel. Throughput is bound to suffer to a certain extent but in most cases it should be ok. For example, in one of the instances that I know of, a throughput of 500K (VPN) was being attained using a 806 connected via a T1! That was with all traffic being encrypted. Things changed for the better as soon as more restrictive crypto access liists were used.
