Dont know about the diff but i got my atlp quads on last week. Drones like crazy in low end rpms. High end sounds fantastic. I am now forced to drive at 3k rpm on freeways just to avoid the drone.

Street driving from stop to go on red lights can be brutAl.
I installed a 22" magnaflow res as close to my cat as possible. Didnt change much

I dont think age has much to do with it, Im 18 and got the car a month or so before I turned 18.. but I think Its all personal pref.
Some people like it loud as all hell which I mean thats Ok if you have a civic. Plus I dont want to draw to much attention to my self, not that the ATLP wont, but it wont draw as much..
or atleast I dont think..

Also What res would be recommended for the ATLP? I remember I was reading a thread but I can't remember where it was.

greddy all the way. Its loud, deep and cool. yes there is drone, so power thru it.

heyy wats up guys i have a 2003 tl and i wanted to buy a greddy 2 evo full cat back exhaust but i wanted to no if it will fit on mines please let me know asap ....

I had a GReddy and the drone was horrendous. Now that I have the ATLP base, it's much more tolerable inside the cabin. Besides the sound, I really liked how the ATLP sits really flushed with the car.