I guess I'd have to ask... what do you want out of this? Hobbies are great, but make sure that you've got yourself covered now. Invest a bit of that scratch you use to upgrade the stereo so that you CAN do whatever you want hobby-wise as the years go by. (I didn't)
I have a very hard time jumping on the car audio extremist bandwagon. Just doesn't make sense to me. In my car, I want the best sound possible, ideally, I should have all the volume and more that I need with zero spilling out to other folks (with the windows up and such.). Like has been said before, a car is an AWFUL place to reproduce sound.
140 dB?! I realize that's nowhere near what some of these systems pump out, but come on. To what end?
My vote: spend the money on the best "sounding" sound you can get. With a target audience of a carload and -close- neighbors (cars next to you maybe), and not a city block. (And by best sounding, I mean the best reproduction, not the -most- sound, tightest bass, etc.)
If I can give a slight parallel. I'm an actor approaching 30 here soon, and I'm already feeling pain from things I've done in past shows, feeling the strain of years of having not warmed up my instrument. I'm wishing that I'd taken the time to take better care of myself. Same goes for your ears. Seriously, man. It makes absolutely zero sense to me to spend all this money on a stereo that you have to wear earplugs/covers to listen to. Call me crazy.