Since you put it that way. Then it'd be well worth it to buy that kind of technology to run those hard core games. Of course even if you do all the things you said to a pc, MOBO, CPU etc, space, fans, you're still probably going to experience some LAG?? Wouldn't that be something, spend 3K on a PC and still get LAG.
I've noticed users testing their PC's by placing numerous units on the map with Arma2 and they still get LAG. My main thing with building a high end performance PC would be to play great multiplayer ArmA2 games with ACE and all that stuff. Have fun with other players and experience those huge missions without experiencing much LAG.
So lets see, CPU $1k, GPU $1K, your spending alone $1K on each component in your pc. Then not to mention, it goes out of date in like what, a week? So uhm, where is the good part for us gamers in high end performance PC's?