My mother's van was recently rear-ended at 40 mph, SHE was perfectly fine

, but the van was totalled (today we have a very nice '05 Sienna in place of the Oldsmobile). What does this have to do with my Camry? Well, my mom had a nice Alpine deck with Memphis Audio speakers put in her van prior to the accident. Sadly, one of the rear speakers did not survive the crash.
When I put in the Alpine deck, the instructions from InstallDr told me to bypass the stock amplifier. I thought that'd be alright, but I noticed a decrease in sound quality without my stereo being amplified. Sure, the Alpine was MUCH more configurable and customizable than the old stock CD player but I still noticed the under-powered characteristics of the sound quality.
So what I'm wondering... is whether or not it is possible to use my Alpine deck with the stock amplifier to perhaps make it all sound better!
Thanks a lot!
-Mike