1. if you are getting a dfi board you HAVE to have a 24-pin psu. they dont support 20 to 24 pin conversion. i have a 535W enermax which has a 20pin but then a 4 pin right next to it comming DIRECTLY from the psu. that is ok
this also is SLi ready and has 2 fans to keep it cool.
2.DFI boards a GREAT for OCing. i would also say Ultra-D because you can mod to SLi if need be
3. I would go with a case that has at least 2 fans. if you want 1 that will last a while tsunami dream is pretty schweet.
so psu AND case total about $190
4. eVga 6800GT FO SHO
5. on board sound for the DFI is really good but if you are pretty serious about your gaming sound go with a creative audigy 2 zs "something". there is plat, plat pro, gamer, and value. some gnarly deals at zipzoomfly.com with liek $50 mail in rebate