Hey guys i want to upgrade my geforce mx 4000 128 mb agp to newer agp card. But i m confused between Nvidia 6600 GT and Non-GT what are the differences and what about the cost, can any one tell me. Are these cards 8x will perform good on my 4x mobo. I m using 2.4 ghz 512 mb ram, HIS VIA mobo 80 GB HDD do i require to purchase new SMPS. HELP ME.