$200 is high for a 6950 and you'd be better off with a new 7850 which is more powerful for under $200, for $150 its ok.
It looks like you have 5 gpus, why do you need a new one? I'd suggest the 7950 or the 7870 since they are extremely good price for what they offer.
I do have 5 gpus but I have CF 4870s in one system. Thanks for the fast reply, I'll look into that.