With my HD 6950 unlocked/overclocked, I can play The Witcher 2 @1920x1200 and 40fps w/ everything on except Ubersampling (which makes my frames drop to around 25).
There's also the GTX 560 Ti that's close to that, and both will cost you around 250$. If you want a bit more, then you can always...
The Radeon HD 6950 2GB fits your description exactly (there is one @229$ after rebate on newegg, but I guess it depends where you live), but if you want to stick with Nvidia I hear the GTX 560 Ti, as you mentioned, is good. The 2500k should handle gaming just fine no matter what card you get...
The Sager NP8170 should fit your needs.
http://www.xoticpc.com/sager-np8170-clevo-p170hm-p-2971.html?wconfigure=yes
Edit: you can also check the NP8170-S1 which is basically the NP8170 but upgraded and with a rebate : http://www.xoticpc.com/sager-np8170s1-clevo-p170hm-p-2982.html?wconfigure=yes...
:rolleyes:
On topic: I got an hd 6950 2gb, it unlocked very easily and I got to 921/1550 Mhz @ 1.115V...
You might not get the same results but with that much overclockability and the shader unlock,
I say definitely go for an hd 6950 if you like overclocking (you should try to find a reference...
I unlocked the shaders on my Sapphire HD 6950 2GB and overclocked to 900/1500Mhz @ 1.1V
I'm trying to see how high I can OC it with higher voltages right now, I got 921/1550Mhz with only 1.115V
Anyways, it's really awesome : for only 275$ + tax and shipping, it's probably the best...