I know what you mean on cards, I'm fairly lucky in that I've never had a bad nvidia card, where as I had a stock ati card cook it's own memory due to bad design and inadequate cooling, that put me off ati for a long time.
However the past few years have seen great improvement in them and personally speaking a lessening in nvidia stock cooling. (esp in the mid range)
And all told I do prefer nvidia, it's also down to the fact that two of my key MMO's both used PhysX and I do a couple of things with cuda too.
I've recently picked up a 2nd hand Asus DirectCU II gtx560Ti (from Useitnow) and I'm very impressed so far.
Probably the gtx570 is worth a look esp if you get a new high res screen
http://hexus.net/tech/reviews/graphi...ng-best-fermi/
The Asus 570 directCUII looks good and great value
http://www.scan.co.uk/products/31280...-dvi-i-dp-hdmi However it is a triple slots card so it is going to take up space.