Some good suggestions here.
I like the gkay09 list the best.
Flight sim, and I assume it is flight simulator-X, are very dependent on the cpu, and particularly multiple cores. The i7 with hyperthreading is heads and shoulders above the rest in that respect. The price delta of a i7 system for cpu, mobo, and ram is about $150 more than an equivalently spec'd Qxxx system. In this case, very much worth it.
Going with a single drive initially is not a bad idea, the prices of hard drives are still going down, so adding one later when/if you need more space is not a bad idea.
The gtx260-216 is a very capable card, and should run everything well. In the future, when 40nm parts arrive, the upgrade path will likely be to a more capable single card instead of sli with a second gtx260. For that reason, there is no need to spend more up front on a psu capable of running two vga cards. A very good unit would be the PC P&C silencer610, currently at $79.99 after rebate:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817703005