How about a GTX275 instead of a 260 or 280?
Don't know about over there, but here the 275 is hardly more than a 260 and the performance is close to a 280.
I highly recommend Scythe Slipstream fans (you might have some in mind already) - I have the 1200rpm versions and they're very quiet, the 1600 or 1900rpm versions push a lot more air but are noisier, probably better for you if you're using a fan controller. The stock 900 fans are pretty bad IMHO.
Don't know about Windows 7 myself, someone else may do.