Justedbin, unforunately for both me and you, its very hard to get a straight answer on this topic. The people who want to play the games now at great FPS will reccomend a X1950XT or a 7950GT, and to a lesser budget a X1950PRO or 7900GS. The people who want to be futureproofed will choose the 8600GT/GTS (for your budget) and play today's games at similar frame rates to the X1950Pro/7900GS, but will be able to play DX10 games at however low framerate it is. Unfortunately, there is little to no data available on how the 8xxx series will run pure DX10 games (not patched), so for me it is hard to justify spending more for something that, by the look of performance charts of DX10 patched games, won't be very playable.
In the end, the choice is up to you, it depends on your view on things, but with that budget (similar to mine) I would suggest sticking with DX10, and going with eVGA if you believe you would like to "step-up" the card within 90 days. Also just a word of caution, if you do get a DX10 card, you will need to use Vista (99% sure