I too was saddened by how poor the base stereo sounds, but wasn't too thrilled to pay for a dash kit to install an aftermarket head unit.
So I bought myself some xmas presents from sonic electronix and will be installing them tomorrow (providing I can find a line output converter locally, bought a 5ch amp that takes speaker level inputs but not for the sub channel)
Here's what I went with: Power Acoustik GT5-2500 2500W Max, 5-Channel Gothic Series Car Amp Kenwood KFC-C6894PS 6" x 8" 3-Way Performance Coaxial Car Speakers e2 ECAP1 1.0 Farad Digital Capacitor - Sonic Electronix Alpine SWS-10D4 (sws10d44) 10" Dual 4-Ohm Type-S Series Car Subwoofer
Also picked up a cheap sealed box (I listen to mostly metal, so I don't want/need the booming bass of a ported box) And yes I know the amp is junk, but I was doing the upgrade on a budget :/ Unfortunately I bought the metra connector harness as well, oh well, easy fix.
Will hopefully post how it went and any tips/hints I might have figured out along the way. OP will definitely help with removing my door trim without wrecking it. Thanks Ace72Ace!