Upgrading internal amp?

My sister has a 2004 civic with a factory system.  I recently installed a Directed Electronics FM Modulator (RFM100)w to connect her Ipod.  It has great sound quality, but it loses a lot of volume.  I would say a good 30%.  Is there any way to upgrade the amp built into the HU?  there are a few places around town that repair amps and headunits, could they do this?  I don't want to add an external amp to the factory HU, and she does not need anything more complicated.  Trust me, she will die.

u need a audio booster to go between you ipod and your fm mod i use this one alot http://www.audiooutfitter.com/store/71021/AB1.html 

you can also eliminate the fm mod and go with a direct input AUX style and get the best sound possable from USA spec http://usaspec.com/aux2.html  $79.95 or direct ipod interface http://usaspec.com/ipod.html $149.95

Touche'.  Thank you.