I am running an AMD quad @ 4 Ghz, 8 GB DDR3, AMD 7850 2GB DDR5, SSD and I can play everything... Blitz, Ridge Racer, Cotton Boomerang, Die Hard Arcade, etc.
We play PC games on it as well, Tekken vs SF, Mortal Kombat, Super SF IV AE, MUGEN, etc.
Intel is superior here, sure, but can you play just about everything regarding emulation with a nice AMD system..? Absolutely.
I priced out what I wanted and the comparable Intel system would have been ~$150 more due to cpu, SLI/CF capable mobo, ram, etc.
With that said the next build will likely have an i7 just to mix things up a bit.

Jason