Hey Anders --- I have a GTX580 which seems to handle the DX10 fixer quite well at 8xsgss. I haven't checked the gpu temps since I went to it, but I do turn the gpu fan up to 75% every time I fire up FSX. I have not seen any spikes or weird graphics artifacts which is what usually happens when the gpu is overheated. Also, I have no car traffic, and my UT2 traffic is at 45% and airport traffic at minimum. No other traffic or airplane labels. Autogen is at dense.

Your Haswell build with a Titan or even a base 780 will certainly take care of any graphics concerns.

I would never go back to DX9, even though I had it looking quite decent, like yourself. The DX10 fixer, as you mentioned, provides more crisp clear graphics with better color and smoother game play for sure.

Good luck on the new build!

Bruce