If you want to build a PC, probably starting your own thread would be the best bet to get people's opinions, otherwise I wouldn't mind working through PMs. Here's
a wishlist of an i5 build I put together about a month ago. It's just missing an OS, if you need that included in your budget, I can refresh the build and try to squeeze some money out. An $800 build these days should be able to max Crysis and most new games btw
I wouldn't concern yourself with the memory interface bitrate if you're dealing with newer $100+ cards. Like the nvidia gtx 260 is a 488bit GDDR3 while the stronger ati 5870 is 256bit with GDDR3. I don't think it's as relevant these days with new cards as it's not a spec to really compare things with since it's different hardware. The 1GB refers to the amount of video ram is on the board. If you want to compare cards, your best bet is to look up different benchmarks, not just look at the specs. A $180 ATI 4890 isn't really a deal though either

that's about standard price (should be even lower with the newer 5 series out)