Stock audio components

Hellooooo!

I don't like the sound in my 2003 SRS Tundra (Toyota system w/ 6-disk changer) and would like to upgrade it.

I wonder if anyone "out there" could give me a list of the current stock parts and sizes that I could take to the car audio place.

I know I have a 2DIN head unit and, what is it, 6 speakers? I'd like to put in a very highend head unit cd/tuner (don't need multi-disk), a 6-channel amplifier, and very good replacement speakers. Think LOUD Boston, Radiohead, Linkin Park, Zeppelin....to.....not so loud (but CLEAN) Samuel Barber and Dvorak.

I guess my biggest problem is that I don't know the speaker sizes (diameter and depth).

I'd also very much like to find a head-unit that doesn't look like so "clubkid-ish". Most of the units I see out there now are obviously designed for the 22yr old in a highrev slot car. Don't get me wrong, there's nothing wrong with that, but I am just getting to be an old bahstad I guess.

Thanks extremely in advance!

As far as speakers go, i put in a pair of Sony three ways and was happy for a short while. Now i need components. www.Crutchfield.com has the speaker sizes and what fits. 6.5 or 6.75 in i think. www.tundrasolutions.com has a list of component speakers that fit depth wise. I want Infinity Kappa... Im not a head unit kind of guy, so im running my amp off the stocker.
My only question is why a six channel amp? The tweeters from components are powered thru the same channel as the front, but seperated with a crossover. A four channel or 5 if you want a sub should do it (or a 4 channel and a single channel amp).
Lastly i am by no means a stereo genius. If anyone wants to dissagree or correct me please do.