Gtx 550 ti or 650?

650 is the way to go.

Very similar performance. So might as well get the 650 as it's newer and uses much less power.

http://www.anandtech.com/bench/Product/536?vs=681

7770 is already better than 650.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This is cheaper than 650. So just get it.

In the review i linked you there is a stock 7770. I linked you Ghz edition and AMD has released new drivers 12.11 (7+version) and in each one great improvements !

Good Luck !

Yeah if your o.k. with a AMD card the 7770 is a good choice.I did not mention it because was not part of your question.

Out of stock!  

Well it will be soon. Its been 16 hrs out of stock so just wait 12 more. That happened 3 times already .

Edit : http://www.newegg.com/Product/Product.aspx?Item=N82E168... Consider this too

Sounds like a good plan.