I upgraded from http://www.newegg.com/Product/Product.aspx?Item=N82E16814130441 to http://www.newegg.com/Product/Product.aspx?Item=N82E16814130660 .
Both are amazing cards and max out pretty much every game on the market that i have played. (currently maxing out Skyrim with my new 560. might be able to with my 260 as sell) The 260 is deactivated on newegg but im sure you can find it somewhere for $100 or less, pretty good card for the money,lasted me several years and would probably last me a few more, but wanted to upgrade since i had the money for it. The 560 is amazing, definite buy if you don't mind spending about $200 for a card.
Stay away from the 250,450,550. You want something that is at least 260,460,560 or higher. The x50 cards are not meant for gaming.
Edit: sry, the period i put at the end of the second link screwed it up lol.