Yes. I have a half decent amp built into my soundcard (Asus Xonar DG) and all they do is get louder, but it does not really change the sound at all. They are only 40ohm and relatively sensitive.
You should get the Asus Xonar for about $20 and sometimes its only $11 with rebate. It's a huge upgrade from onboard sound.
Edited by Supertoaster - 9/18/12 at 3:06pm