See I'm actually curious about this one too, because in the past I've not really given a crap who made the card so long as it had the core I was after. Where's MrL when you need him?
I was looking at getting
something like this for my next box which fits snugly into your top-end price bracket, at least at UK prices. It's clocked to 600MHz since I can't get round the idea that short of water-cooling the damned things the 650-700MHz cards are going to need some pretty effective air-flow which in turn means noise. For a gaming rig that's not too much of an issue, but it's still a bit of a pain to have a light aircraft take off by your crotch every time you fire up CoD4