If he's running 3 monitors, you're most likely correct that he's running ATi. The Eyefinity craze is much more prevalent over there than whatever nVidia's equivalent is.
Unfortunately, you caught me at an awkward time. If you didn't have the Christmas deadline, I'd point out that Microsoft is resurrecting their flight simulator series soon with Microsoft Flight.
Short of that.. Hmm.
Rise of Flight would probably scratch the itch. It's a pretty authentic and impressively detailed WWI sim that supports a good array of enthusiast hardware from what I understand (not having any serious enthusiast hardware myself).
Again, looking on the horizon a bit, the guys who brought us World of Tanks are working on World of Planes.
As far as controllers go, I enjoy my Thrustmaster 1600.M as it's pretty comfortable and nicely configurable, with a good build quality. But it's definitely a gaming stick rather than a particularly sim-oriented one, and it's not a pedal/throttle setup, which it sounds like you might be looking for. I think only Thrustmaster, Saitek, and Logitech are really even making flight sticks anymore, and they're all pretty well regarded from back in the day. When I was shopping for my current stick a year or two ago, reviews seemed to indicate that Logitech's more broadly marketed sticks' quality may have suffered some in recent years, though I'd be shocked to hear their higher end stuff did the same. I harbor some prejudices against Saitek from over a decade ago, but they're probably the most "serious" of the 3 anymore. IIRC, they were the only ones from whom I saw any yokes when I was looking (not that I prefer yokes, but your friend might, depending on what kind of airplane controls he wants to feel like).
There's another game or two that I don't have direct experience with that I feel like I should have mentioned, but I'm drawing a blank. I'll look through RPS later today at lunch or something and see if I can jog my memory.
And Lex, the stuff I've seen from Microsoft Flight will surprise you, then.