Hexx, the guy is full of shat. There is a reason they make liquid cooling systems for pcs, for Kirks sake, lol!
Two fans with a high speed processor and a top o the line graphics card AINT gonna cut it. TRUST ME.
And all powersupplies are NOT created equal. Some have multiple fans to run cooler. Some run very quiet. Some cheap ones run hot and noisy. Do some research. Or go with what Kroma said. They guy at the store is just trying to sell you what he WANTS to sell you chief, same as anywhere else you go.
Goto
www.overclockers.com and read what they say about case cooling. And look at all the homemade water cooling systems people have made, there is one designed like the cooling tower for a nuke reactor for christs sake. All that work aint gonna be done if pcs only need 2 fans, lol!
Hell, my FACTORY laptop im on right now as my desktop just went tits up the other day is a P-4 2.8 with a GF 5200 and it has 3 fans in its wee case and IT shuts down all the time when Im gaming due to overheating! Ive gotta keep it where the exhaust fan blows out into open space, I have to put spacers under the back of the case so it can suck more cool air and it still cuts off sometimes. Im gonna have to resort to what I did with my Commodore 64 back in the day... buy a regular fan and put it next to the case and keep the case cool, and freeze my ballz off the whole time Im using it, lol!
The price we pay for computing bliss.