too much stupidity in this thread...
is there such a thing as futureproof? not in video cards. if you're willing to sacrifice enuff (resolution, image quality, etc), people are still managing just fine with their geforce3/radeon 8500.
bottom line is a mid range card now (6600gt) is a low end card in a year or so. as good as the 9800pro/xt was in it's 'heyday', today's mid-range card is a better overall performer.
is sm3 a good thing? sure... but do we need it it's not really implemented at ths time, and in reality by the time it is, the whole spec only allows for a couple things not possible in sm2.x..... there simply is not the difference as there was from sm1 to sm2. if anything, history has shown us - hell, PROVEN, that regardless of sm-this, sm-that (remember t&l? or how about all those "cool" features which turned out to be nothing - truform, anyone?), by the time sm3 becomes the "target" api, today's BEST sm3 cards will run those games with mediocrity at best.
there really only one thing that for certain -- that by the time ut3 comes out, there will be a midrange card that is reasonably priced (likely half the price of what i've paid for my x800s and nv40) which will outperform my (current) 6800GT. how is that for "futureproof"?
where will that leave the 6600gt? in the bargain basement. sure.. sli will help, but you'll be able to purchase a faster, single card for the same or less than what you'll be able to get a new 6600gt for (look at current prices of new last gen cards... only good for the uneducated who don't know better). a 6800gt now and upgrade to sli in a year would be a more reasonable argument (tho not without its faults) imo.
as for ati vs nv, who cares? while there have certainly been times when one had a clear advantage over the other, this is certainly not the case this year. differences in performance/IQ are so minor only the anal, or for those with far too much time that they would rather scrutinize screenshots rather than acutally playing a game would make a huge issue of it.
the only sound advice is to get the fastest, most stable card your budget allows for, and hang onto it for a long as you can stand....
i would agree tho that if you can only afford a midrange card, nv is the only option. ati has dropped the ball completely in the budget/mid-range segment (and frankly they also dropped the ball in the highend for not living up to delivery dates, and not having a supply after they actually shipped something -- hopefully that will change), but the reality is, in the future, today's best mid-range card will still be barely adequate compared to future generation cards....