Aside: $3K is a HUGE budget for a gaming system. Does he really want that or is he targeting what to spend to get a system that runs modern games on highest settings and will last a few years -- which would be more like $1K than $3K. (Ok, I'm a whimp and the first $3K system I bought was the last one I bought -- pentium 100 based).
Suggest an I5-2500 or I7-2600 based system. Video card based on your pocketbook and Tom's "best graphic cards for the money" article which shows great cards for $300. Could be built by Cyberpower or some other.
I think unless you are good with PCs and mechanicals that going for a $2500 water cooled system is not the right answer. But would certainly give bragging rights. I would avoid the extreme overclock versions "Overclock CPU 4.5GHz to 4.8GHz" -- you want a few years of life and stability and gaming doesn't really seem to need or use much more than stock i7-2600 performance anyway.