Hey all,
As some of you know, I just put in my new deck a couple of nights ago...
Here are my thoughts:
1) You don't have to to get the plates --
I started my stereo mod the 'other' way. I got the speakers first (Pioneer TS-6865 3-ways). 2 pairs, and that made a nice difference over the stock speakers. With the stock stereo, the sound was noticeably better.
2) Once I put my HU in (JVC mp3), I noticed how phenomenal car audio can be. My sound is great, and that's just with 4 nice door speakers and a new HU.
3) BYPASS THE AMP! It will take a lot of work if you don't buy the 'exact' harness, if it exists. I bought a kit, last digits are 4514, or 5414 or something. Same on all brands of harness. It's a bypass kit with a couple of cables which give you two options. a) Bypass the amp b) go through the amp. The kit also included a power harness.
The kit was great, cuz it meant I could do an install which wouldn't cut into the factory wires, and leave me able to put the stock system back together easily.
Anyway - good luck with the system. It should sound great the way you've got it set up. You can always upgrade later.
Brian