Audio Upgrade Project Sanity Check

[Cunningr]

Hi All,
I have several projects on going and planned for my ride, one in which is sound system upgrade. I was going to do a double DIN set up but wife is like the car is a classic don't do that, so redirection is a single DIN to make it easy to go back to factory gear. So here is my plan just wanted a bit of feedback and maybe some thoughts on speakers.

Current setup 00S:
Stock Becker HU with 996 6 channel amp, 6 Chanel CD changer, Factory door speakers, JBL GTO 4" coaxial in dash. Rear speaker kit with Pioneers being this week's project.

Planed Gear:
HU Pioneer DEH-PRS-80
Door speakers Kicker 6.75" DVC subwoofers shallow mount
Rear pioneers from kit remain same
Dash speakers thinking of upgrading to separates or better coaxial
Amp JL Audio 5 Channel RD may change to the small units do a 4 and a mono.

How:
Door speakers I bought used door speakers with factory Nokia box $40 for pair. Will use the box to cut up and install the door subs.

Amplifier bought a old M490 AMP for $20 off ebay. Will use that to dis-assemble to get the connector out and use the factory bracket to mount after market amp.

Dash I use the CAI mounting rings little pricey but really easy to use.

Rear is a PnP into the shelf unit.

So if you read this far you are interested in the project:
Thoughts on plan, equipment, ect...

Alternative speaker configuration or opinion on a HU/speaker setup with 6 channel amp.

Going for the best sound I can get but not a competition setup.