My msi 6600gt is quiet, and their cards usually get good reviews in that area. So look up msi 6600gt's and 6800nu's, which should both be quieter than most the competition. Not sure what other brands around that price range are quiet as well.
[Edit:] My card's agp btw, but since the agp and pci-e versions of the 6600gt are so similar, I think your results will be similar. Also, the reviews I've read of 6600gt's(pci-e) note that msi's is noticeably quieter than other brands. Anandtech should have an old review on this if you want to look into it.
Helpful. If I wind up with some stretch on the budget, I may be back with more $$ in the budget for a good card.
(I'm at about $1600 now, and think I might be able to get another $400 into the budget...
presently budgeted at:
AMD 3500
MSI 6600GT
which are both at pretty good price points.)
I haven't heard any noise complaints with the X800XLs, and considering that they can be had for $270 (only $20 over your budget) I can't find a good reason not to get one of those. I mean, it's going to be nearly twice as powerful as the 6600GT...