Hmm so I understand the 4870 is supposed to be slightly better then the 260. But I thought the 9800gt2 actually had similar performance as the 280, which is better then the 4870. So why the 4870 over the 9800gt2? And how do those SLI configs run?
My 9800 GT came with Physx, it's not just limited to the GTX 260. But for that budget, I'd suggest the 4870 simply because, a single GPU setup is mainly better than a dual GPU (such as a 9800GX2 or 9/8800 GT's in SLI.