Over the weekend I added the amp below to the stock headunit and speakers.
Sony XMS400D Compact 4-channel car amplifier — 45 watts RMS x 4 at Crutchfield
To say I'm "pleased" would be an understatement. This this pushes the stock speakers with no distortion all the way to "40".
I don't listen to much "rap" or super bass-y stuff, but the stock speakers can vibrate the mirrors nicely.
The mids and highs sound very full, and complete.

I was considering replacing the all door speakers as well as the dash tweeters, but after this upgrade I'm gonna enjoy the stock speakers a bit longer (i know, I must sound totally loony for saying this).
I mounted it above the glovebox and with some proper mounting, it sits securely and doesn't get too warm.

Thoroughly recommended!

 

How did you splice up your connections? Difficulty of install??

 

TO make it easier and cleaner (more stock appearance), I ordered some Metra harnesses on amazon.
This way I could easily remove the amp if I need to take the car in for any warranty work and the techs would be none the wiser.

I also used solder seal connectors and bundled it all up with black electrical tape. Seriously, if you didn't know it wasn't stock, you'd think it was!
The only wires I had to run were one power wire to the fuse box, and a ground to one of the many metal dash locations.
I used this member's suggestion as it saved me having to run a wire thru the firewall

All in all, from start to finish I'd highly recommend this upgrade.
The GK5's stock radio (even with the "upgraded high-power" system) leaves much to be desired.
With this amp you'll get a solid 45w RMSx4 over the stock 28ishwx4 RMS

 

Bassguitarist and I have both installed compact Kenwood amps in the same place too.

 

I take back the compliments I've given the stock speakers.
After a few days, the dash tweeters are far too shrill and piercing to enjoy music at any volume.
Hopefully the Pioneer components are better (they should be!)
Pioneer TS-A652C A-Series 6-1/2" component speaker system at Crutchfield Canada

 

Thanks for the video, this is great . Anyone recommend coax over components?

 

Components > Coax's. Always.

 

That big a difference eh? Well I'mma start saving my pennies now