the Intel little valley and the new Atom boards are very popular and should meet all your requirements. they are cheap, consume very little power, and perform very well. the CPU clock speeds are a little less than your 1.5GHz, but they should still perform as well or better as the via C7.
I use the Intel little Valley D201GLY2A with the M2-ATX-HV. I run RR with IG4. it has handled every program/component I've up to it. I have experienced no problems at all with this board so I have nothing but good things to say about it. the new dual-core Atom boards are newer, I probably would have bought that instead but they weren't out yet when I built my system.