Currently I'd say 2500K/2600k if you run modern apps that can use hypertheading (not FSX) then the 26 is the best candidate
And a GTX 580 if you can. Otherwise a 570. Apparently the extra for the 580 is really worth it (that's if you run the resource hungry FTX stuff.
Still a build based around these 2 items with quality parts will get expensive quickly. My last mock up build saw me at the 3.5 k mark. You can do it cheaper but.... Actually that may have been with a monitor aswell?