The best absolute advice is Quincy's - get some cable extenders and get it out of the room.
If you are set on having it within arms reach than the costs for keeping things quiet are expensive. I decided to have my computer close by and spent about a $600 to $700 USD premium on quiet components.
This included
Quiet power supply (quite often the biggest culprit)( I used Seasonic)
Specialized Quiet Case Fans
2 Ultra Quiet CPU Fans (Thermaltake)
1 Zalman quiet VGA Fan
4 Hard drive enclosures (Quietpc.ca or com)
Lian Li make some of the best cases on the planet (Check out the Lian Li PC-73SLB)
I didn't use it on mine, but the Zalman liquid cooling is pretty cool but you will probably need two units if you have two CPU's.
When all is said and done you are looking at a lot of scratch but it does make a significant difference.
Check out these sites for more info;
www.silentpcreview.com www.quietpc.com www.endpcnoise.com
do some google searches as there are other sites, hope that helps.