See the form in my sig - edit your post to match it and we'll be able to help you out. To answer your questions though, a 5850 and an i7 860 should be good.
Ok, here's some more details:
Approximate Purchase Date: By year end 2009.
System Usage: Mainly Gaming
Preferred brands: Intel
Monitor resolution: 1920 x 1200
Additional comments: After reading various reviews, I've come to the conclusion that SLI/CF is required if I need to play games at the above resolution with AA / AF turned on and with the highest quality settings. Please let me know if this conclusion is correct.
Also, I don't really know what is the minimum fps needed to qualify as "smooth" gameplay. Is it 30? or 45? Because it drives me mad when games stutter during action sequences and I would like the minimum fps to be high enough not so that games do not stutter.