What's the specs of the new computer? If it's runs hot it's very DANGEROUS to let the CPU fan shut down when the Computer is in standby, my friend nearly fried his 1G T'bird in that way.
U could get a cooler computer so u'd need less fan power by undervolting or underclocking the CPU (let someone else fill in that info here), but personally if u're not running the CPU at full load all the time I'd recommend http://www.vcool.de
Vcool as it issues a stop command to the CPU so it's idleing but it shuts itself off.
And I'd suggest u'd look at other methods of silcencing the computer like adding acoustic foam and changing fans etc, these are on the right side of the diminishing returns graph
, this site has a lot of stuff about that as well.