V2 sli looses in image quality against all youve counted, but the image quality is still very good in glide and could be worse even in d3d. It is the most compatible of all and performance of sli is between v3 2000 and v3 3000. Its slower than TNT2 but much faster than TNT and savage4.
If I had a sli with such a fast processor as you have, i wouldnt upgrade. if you have to much money, get a TNT2 for d3d and keep the sli for glide, thats still the best solution.