Kinda on a budget but the 6600 GT has core of 500/1000mhz Effective thats good right?
IS this a good card to overclock?
Well it depends on the cards architecture and memory. That's standard for the card yeah.. whether it overclocks well or not you'd have to google up because I don't know anyone here who has one that's tried OC'ing it...so itd be anyones guess.
ABit does indeed provide some of the best boards for OC'ing but you should probably check the specs on ABit's website and see what the BIOS layout is via downloading the manual.