[G Rahn]

As bl420 mentioned, there is no comparison between a 50X4 HU rating and 50X4 external amp rating.
And that 22 watts RMS rating for the Kenwood is only correct when you manipulate the numbers. It's a lot closer to 12-14 watts in real life. There's even more to it than that, when you factor in dynamic power usage at lower frequencies.
There are a couple of (Full range switching) exceptions, but you won't find a 50X4 amp that even comes close to the size of a single DIN HU, so that ought to tell you something. If they could be made smaller it would have been done long ago. OK... they can, they don't, they will... just not at the moment
If you want power, you need an external amp. A good 50X4 amp will provide more than double the output of an HU. Four to five times the output is more like it.

I'm not sure what you mean about the amp being noticeable, but if you are going with an aftermarket external amp, make sure it has enough airspace around it for proper cooling.

Cool with gutting the car for soundproofing- wish I was there to help you out. :2cool:

 

[G Rahn]

I remember the days when I gutted my car to sound deaden it. It was a pain, yet satisfying knowing that I did it myself

Just out of curiosity, what did you do with that headliner (if anything)?

 

[G Rahn]

I have used Second Skin Damplifier and Regular Dynamat. Both are good, but the second Skin product is a better value.
Here is a link to a review of some of the popular sound deadeners-
http://www.sounddeadenershowdown.com/

I'm thinking of taking out the headliner an putting velour fabric on it to cut down on reflections. The leather and hard headliner sure has the signals bouncing around.