Amp Speaker Question

bpd138

I have a NOOB question so please don't laugh!

I have installed a Kenwood DNX8120 in my new Z. Pictures are in one of my albums. I have (don't laugh) Polk DB651 6" two way speakers in the doors and Polk DB351 3.5" speakers in the rear. I left the stock "tweeters" in the dash for now because I don't know what to do with them.
Using the advice of another forum member I have purchased an Infinity Reference 475a amp, which I haven't installed yet.

If I am correct the Kenwood head unit is rated for 22watts continuous output for the four speakers. My speakers are rated at about 45watts continuous output. To my untrained ears they don't sound that bad hooked up to the head unit without an amp.

Okay heres the question(s).
If I go through the trouble of installing the amp;
1) Will I notice that much of a difference in sound quality?
2) If i don't hook up the amp will I damage anything?
3) Any suggestions on how and where to mount the amp and also where to run the power wire through the firewall?

Once again you guys are great.
Take care,
Willie