replacing factory infinity amplifier?

I am needing to replace the factory infinity amplifier in my 2003 Dodge Ram 1500 4 door. I Added the following in and under the center armrest - - Audio Control 3-way Line Driver - Alpine 310 brain - Alpine XM reciever - Alpine GPS I am now out of room for adding new equipment. I was under the impression that upping the line voltage to the factory infinity would raise the output to the speakers, (Boston Acoustics in factory locations) all this has accomplished is a slow death of the factory amplifier. I would like to replace the amplifier with the kicker "upgrade" amplifier through Mopar for Plug N Play purposes, but I don't think that amp will work on an '03. I have no room so whatever I buy needs to fit in place of the factory amp in the dash. Any ideas? I am running a MMATS 1600.5 on 2 10" pioneer premier pro series under the back seat. I am just wanting clean sound (Digital?), and compact size. Thanks for any suggestion!"Mopar to ya!"

Arc audio has some really small amps they make. www.arcaudio.com not cheap but they are designed/built well.