Great topic! I must have spent an HOUR on Sunday night reading other forums and posts about just this very topic, and I have something for you on this I would like to share - as it makes my mind up 100% It's quite simple actually. Buy a single GTX680 4096GB. Why? XP10 is going to go 64bit "soonish" - sliders to the right time! (Sort of!) What you'll be limited by a lot of the time will be VRAM, so given there will be "no limit" on the X-Plane application's use of RAM means that you'll want to take as much advantage of available VRAM as possible - so that you get more "stuff" on screen. So, this means that a 4096 vs a 2048 will be better yes? Fairly obvious. OK, so why a 680 over a 690? There is a quietish marketing secret about the VRAM on the 690 that is not disclosed. As you already know, it is two GPUs on one card, two cards in SLI on one physical card if you take my meaning. BUT: In order for the SLI-bit to work each GPU has to have it's own local "copy" of the VRAM - which means that each GPU consumes 2048Mb each just for the SLI-bit. This leaves 2048 useable VRAM for the applications, in this case X-Plane. Which means you only get 2048Mb of VRAM to play with. Secondly, X-Plane doesn't support SLI yet, so there is no point getting more than one card - so a single GTX680 4096 it is then! Finally, in terms of performance, if using a GTX680 is like slicing through a log first time with an axe, then a GTX690 is simply going "too hard" and shattering the axe head and then your wrist as a result. What do I mean? TOO much power we ain't gonna use. Not yet. Give me more VRAM today so that I can fill the screen with lovely things. As long as I get 30-50fps I will be as happy as a pig in sh1t. I don't need 120fps, or epilepsy for that matter. I hope that helps - sorry the sarcastic tone, it was not meant that way, more to be playful as I am happy *grins* to post about something I spent quite some time doing some research on and came to happy conclusion - plus I get to save about £250 on the potential purchase of an under-utilised 690!! Cheers James