Low Power Usage dilemma

This is probably not the usual request, I tried to search but couldn't find much about what I am going to write.

Ok, let me start saying that I am a heavy Business Astaro user (6 devices in 3 pairs) and also a very light Home user (SSH, Socks Proxy, Proxy, SSL VPN, some dns forwarding and NTP server, I think that it is).

Anyway, I've been running my home appliance on a small factor PC (Pentium 3 1Ghz + 512MB), not when I upgraded to V8 I lost a bit performance, but that is ok for me, SSH and Socks work great.
I am thorn to switch over a VIA box (close specs to the P3): 866Ghz but 1GB of mem.
The VIA is much quiter than the P3 and has more memory, thou I lose a bit of speed.
Now the nice thing, VIA is 1W CPU, the P3 is a 35W CPU.
Bottom line, I am looking for low pwered solutions, without buying anything new.
So my real question is, is it better to have more memory (from 512 to 1GB) or more CPU speed (1GHz vs 800).
I think I am going to convert to VIA, I've been running them both parallel and I don't really notice much difference.

Any suggestions in the case I decide to use a new feature in the future and it might not be compatible?