@maverick 12 The naming pattern i.e like 6600 ultra,gt and so on is just to differentiate on the diff video memory or the pipelines or the chip and memory clock speeds that they are buit on.....nothin that special just that some have a decent amount of frame rates increase
Btw Since ur Mobo supports the PCI-E Architecture i assume that the 6600 gt u are up against is the PCI-E version as well
So then without any confusion the 6600 gt is a 128Mb directX9.0c 128-bit 8 pipelines based card and it(XFX Geforce 6600 Gt Pci-E Version) retails somewhere from 8k to 10k
But For ur mobo the best would be 6800 gt also if ur into heavy gamin but the cost.....hmmm better not to say or else u shall kill me......

(pssst its 25k approx

)