Let me just say, before the OP goes throwing loads of cash at high end cards, that 1440p is only particularly demanding if you insist on running lots of AA which also makes up a lot of the high VRAM usage. The higher res does a lot to negate the need for x8AA etc, and 2xAA is plenty in most cases. Of course, if you can, it's always nice to max it out. But considering the performance you can get at 2xAA on a much cheaper card, I don't think splashing loads of cash on high end cards is necessary unless the OP wants to max everything and have perfect 60fps.
If it were me, and I wanted to keep things on a budget, I'd go for something like this
http://www.overclockers.co.uk/showproduct.php?prodid=GX-030-C3&groupid=701&catid=56&subcat=1752
And overclock the nuts off it.
Or to push to the max budget
http://www.overclockers.co.uk/showproduct.php?prodid=GX-052-HS&groupid=701&catid=56&subcat=411