Heya guys i really need your help in this one .I have a 6600 GT TDH EXTREAM video card .When i bought it it was a great video card but in those days when you need a small nuclear plant

in order to be able to play the game on normal or normal combined with high details my "grandmma' video " is out of limits.

.My main board have the SLI mode thank God for that and i was thinking about these combinations :
1 - to by a 6600 equal to the one i have , because to by another one is very cheap but i don't know if they will make some difference in a true way.A difference will be but i don't know how big.
2-to by 2 - 7600 - that would prove a little costly but there will be a much bigger difference regarding the performance , but it will be a very good balance between cost/performance
3- to by a WinFast PX8600 GTS TDH Extreme only one because of the price .But i have a problem , I was told that this video card compared to 6600 at its time and the 7600 is crap.Is that true ? I just find it hard to believe.
4- and i was thinking about 7900 to
So if you can help me please do because i really need the advice of a true profesional.
Peace out all.