what kind of x1950 do you have? pro or xt(x)? in any case the 1950, even the pro version, is a lot more powerful than the 8600 gt, depending on the resolution about 20-30%, even faster than the 8600 gts. dx10 doesnt mean much, since the 8600 gt is too slow for it anyway.
if you don't believe me, just google for benchmarks about the 8600gt and x1950.