Smoothest graphics needed for Racing Sims

[NitroStar]

I am looking for a graphics card update that runs very smooth for Racing Sim use. I currently have:
AMD 965 BE
Asus 880 motherboard
GTX 260 w/216 sharers 894mb
Corsair 650 PS (the higher priced model)
4gb ram
win XP

Problem has always been even though I get massive frame rates with this setup, there is still a slight stutter while looking at trees or fences go by and the fences and power lines dont look real. Runs buttery smooth if I v-sync but that causes slight lag in controller input so I don't use it so my lap times are a little better. I hope somebody will comment on the slight stutter at night GPS deal. I do mean it is slight but none the less bugs the fire out of me. I have a HD4850 in a very similar setup and it runs smoother looking at less fps. I want the smoothness of v-sync without the lag.
Are these cards know for this?
Looking for smoothest graphics for racing out of:
1. gtx 570
2. amd 5950
3. amd 5970
Thanks a million!

 

[NitroStar]

All Sims like Race 07 series, rFactor, iRacing, F1 2010. I don't understand the 130 fps stutter and I'm not talking about the stutter that happens from going 130 fps to 80 then to 130 again. I'm being picky here but I should be. The road and controls and all look super good but its not smooth like it is when v-synced. I can get 300 fps in rFactor and the trees and fence has this ever so slight skip while going by.