For mame, the CPU is king. The stronger & faster the CPU, the better.
Without your athlon x2 hertz I can't be sure, but you hould be fine with KI. A cheap directX 9.0 or higher video card might help your system, but you don't need anything special ($50 will do it).
FWIW, Mame prefers intel's "Coretm" brand CPUs (Core 2tm, Core i5, & Core i7) hertz for hetrz, but at least you don't have a P4 (which is slower than atlon hz vs hz except for psx games for some reason). I'd think the phenon II should do okay with mame (closer to the Coretm hz for hz), but haven't seen benchmarks on it.