1) Phenom II X4 and GTX260 run pretty cool. NO doubt about that.
2) with 4k budgtet, I think Coolermaster CM690 should be ideal for you "*www.coolermaster.com/products/product.php?act=detail&id=2908"
Fans in this cabinet:
Front :120 mm Blue LED fan x 1, 1200 rpm, 21 dBA,
Rear : 120 mm standard fan, 1200 rpm, 21 dBA,
Top : 120 or 140 mm fan x 2 (optional),
Bottom : 120 mm fan x 1 (optional),
Left: 120mm fan x 2 (one is optional)-up to 140mm fans
3) 32-bit OS can detect only upto 3.5Gb of ram and anything more than that, you need 64-bit OS.
4) After lot of search some sites are reporting that on extreme overclocking, biostar ta 790GX 128M motherboard's FET (field effect transistors) are getting overheated and resulting in freeze (not dangerous but would limit overclocking potential). Let me try to find a better board.