There is currently no Nvidia DX11 card that is under or close to your budget, at least not on the Egg. Their closest matches are the GTX465 cards on offer at about $250.
The best DX11 card within budget is the HD5770, the next is the slower HD5750.
Why the slavering, rabid, twitching, manic and insane hatred of the poor defenceless, innocent and wonderful HD5770 anyway?
@ct1615: Yes, how the mighty do fall!