I don't think 6000$ PC is a worthy investment for simming - even for current sims as P3D or XPL10. 

Definitely not for FSX...

currently runing fsx on bootcamp win 7 x64 on my macbook pro ( with door open ! Macbooks have problems in coolings )

well,i'm using my laptop for over 2 years and i'm happy with it,but planning to buy a pc and retire my macbook pro.

but a suggestion,never use a computer the way it isnt made for;in my country (iran),there's a little company who makes pc's specified for fsx (i'm gonna buy a 6000$ one in july of them);and i'm pretty sure they're dozens of other ones all around the world!(if there's a one in iran,they're 100 time better ones in other countries).so my suggestion is,dont chase apple for fsx.i've heard once from that company:"maybe the new macpro only give you 40 fps with ASN,REX,NGX in dubai;because fsx doesnt know your up-to-date hardware cause its 7-8 years old!" so dont chase the best graphic cards and other stuff,go search the internet for pro tweaker-pc sorting companies who provide boosted PCs

And what is your point? I'm only asking if the iMac can fulfill my FSX needs with that hardware, not if I should buy a 6000 dollar PC (way too expensive in my opinion though)

Maybe you guys should try the new Mac Pro

I have a iMac late 2013, 3.5 ghz intel7 turboboost 3.8, 4 gb graphics, 16 ram, and well yes i can fly cessna at small airfields at high settings with nice clouds, but to take a pmdg at a bigger airport, noooo chaaaance. 

I would love to know setup for making that 30 fps real,.