PC power supplies will work, but if you get one that's got 5v Regulated and 12v Unregulated (Like most budget and PFC PSU's), you'll have to load down the 5v rail in order to pull the entire max wattage out of it.

I recently converted a 700w PC PSU myself, and had to load the 5v rail with a 3ohm resistor (50w Sandbar) in order to pull max power.

However, the old Compaq Proliant server PSU I just did the other day (500w) has fully regulated 12v, so no loading needed.

I'd pick up a cheap server PSU and convert that instead. Higher power, and less fuss. Plus, cheap!

There's a great read on this over at RC Groups: http://www.rcgroups.com/forums/showthread.php?t=1292514