At idle i've found my Powercolor HD 4890 to be basically inaudible.
Under load the fan ramps up, & is definitely not quiet, but as i use headphones 95% of the time for games, i don't mind.
I presently have a Corsair HX1000 in the main system, a BFG GS 550 in the secondary.
For the Lian LAN (my little relatively portable GHTPC), i use an HX520 presently running a GTX 260.
Pics of my
Lian LAN...basically it's my GHTPC (hooked up to the projector normally; move it when LANing at friends).
It's tight, but fits pretty much all but the uber long GPUs.
Had my 8800 GTX in there when i took these pics; now have a GTX 260 in there.
What case are you getting
Skakruk?