rear speakers low power factory amp? Help! Options

[joy_zze]

I have a
1999 Celica with 4 6.5" speakers and the little
tweeter in the door. I am pretty sure there is only
one factory amp in the console. For some mysterious
reason, the rear speakers are only getting about 1/4
the power of the front speakers, and very little bass.
I replaced all 6.5 inch speakers with JL audio, and
replaced the head unit with a pioneer mp3 player.
Still, the problem persists. I have double checked the
head unit installation, and all seems to be fine. Is
it possible the factory amp only partially crapped out
on the rear speakers? If so, what should i replace it
with? I don't need anything fancy. The front 4
speakers sound great. I'd just like the rear speakers
to sound as good. Should I (could I) just bypass it? Any help/hints you could offer would
be greatly appreciated, as I am getting quite
frustrated! Thank you in advance, Joy

[joy_zze]

Also, my Dad suggested that the problem might lie with the front speakers having a crossover to separate the sound to the tweeters, and no crossover in the back. If that were the case, I would think that other 6g owners with this setup might be experiencing a similar problem. Could this be a design flaw? Would the crossover be included in the factory amp, or is it beyond the amp in the door somewhere. If I removed the factory amp, and didn't replace it with an aftermarket amp, would I lose the front crossover? Thanks a lot, Joy BWT, congrats to all you 6Gers out there. I think they ruined the Celica design aesthetically with the 7th generation -- at least for those of us looking for a little class. I could have bought a new 7th Generation, but I opted for a used 99 with low milage instead.