I agree with the first poster. It's just isn't worth it, whether for the performance or the cooling solution.
If you want a good cooler then just remove the stock and buy an aftermarket cooler, instead of buying a whole graphics card.
Get an Accelero S1 with an S-Flex or Yate Loon 120mm fan (which will cost less than $50), instead of getting a new $300 graphics card (not to mention the $100 you'll be losing in selling the GT).
Hell, even without a fan, the S1 will keep temps well below 60C even when the card is overclocked, which is leaps and bounds better than the GTS's cooling solution.http://www.hardforum.com/showthread.php?t=1261100
In the end, it's your money, though.