SEARCH HARDER BRO.
ebay is ur friend.
you can find used 4870s for less than 100 bucks if u know what ur doing.
hell, you could find a new 5770 for 120 too!
5770 = 4870 while using less power and running cooler.
550Ti cant come close to a 6870. 550Ti's compete with 6850's.
6870's compete with 560Ti's, and 560Ti wins a little bit. but with a small OC, the 6870 can beat a stock 560Ti.