Ideas for new gpu in an elderly system please!

I know that the real solution to this is to upgrade the whole system, but I'd like to do this bit by bit and try and get the most out of my current cpu and mobo.

system is a core 2 duo e8500 with 4gb (2x2gb) on a dfi mobo with a 256gb crucial M4 ssd and win 7 64bit. Current gpu is a radeon 4850. PSU is a corsair 520hx modular

Most gaming is done on the ps3 with a lesser amount on the pc. I bought witcher 2 when that came out last year (?) which was the last pc game I bought and the system struggled with that. What is the best gpu that the system will utilise? Is a 7850 just a total waste? Any suggestions? The plan is to change the cpu and mobo at some point (probably) next year, but I may not.

The Witcher 2 tends to like more threads it seems:

http://www.techspot.com/review/405-t...nce/page8.html

However,the simplest test is to see CPU and GPU usage during the game. If you are finding 100% CPU usage and much less than 100% GPU usage,the CPU will probably be the issue.

i tested a 7770 on witcher 2, with a quad core phenom2

have a read.

i went from a 4870 to the 7770. and framerates doubled or more, it was not jittery and was overall more smooth at all detail settings.
medium/high combination works best on what i had.

the 7850 shouldnt be bottlenecked any, if atall, how would you know it was, unless youve got a newer system to test it on?.
and if you do come to upgrade the rest of your system, itll slot very nicely into it.

Thanks Cat and Stevie, interesting to see the cpu usage on witcher.

I really enjoyed your review Stevie, excellent stuff and very useful to see how a gpu upgrade worked for you when you were in a similar situation! I'll go and try to decide on the right card to get now!