I'll answer your questions about AMD and Intel motherboards, but why not Intel? They're currently leading the way in CPUs for gaming. Yes, I know AMD was in the lead a year or more ago, but things change and people get stuck on the past.
Actually, now that I look at your price range (judging from what you picked, anyway), I'd say your choice in processor is is good. However, the 6400 runs VERY hot, you
will need an after-market heat sink or cooling system of some kind and a very well ventilated case or you'll experience freezeups and frequent bluescreens.
Well, the link to the board you had in mind won't work, appears to be a database error with Newegg. However, other motherboards are showing up fine, so I'll look over some boards and give suggestions.
If you either a) don't plan on using on-board sound or b) know how to do your research on manufacturer sites to get proper drivers and are willing to spend a while screwing around with troubleshooting, I'd recommend:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128327
Gigabyte boards are inexpensive and have never given me a problem. That specific board is also compatible with the Phenom processor, though you may need to update BIOS if you're going to use the new Black Edition (only Phenom worth getting if you're paying that much). That board is also nice for a 64-bit OS because you'll be able to install up to 16 GB of RAM (but only DDR2).
A downside to the board I linked would be that you couldn't go with SLI, but I think SLI's a bit outside your budget anyway. If you decided to upgrade in the future, a 9800 GX2 should be more than enough. The only other problems are the bad default drivers for the on-board audio and the fact that you can only install DDR2 RAM, which really shouldn't matter much.
If you've got any specific needs, like a mATX case or the like, post those here and I'll look at other options.
)
