Well, I've come to a final decision and I'm just not quite sure which way to go..

I'm going to go with the following components for iPod/USB stick use & stealth install:
Alpine IDA-X001 head unit
Alpine PDX-4.150 amplifier (2x150 fronts, bridged 1x300 sub) installed over gas tank

Now, the big debate.. Alpine Type R (SPR-17S / SWR-1022D) or Infinity Perfect (6.1 / 10 VQ) speakers & sub?
Going with Alpine would cost me around $175 less. With the PDX amplifier, would there be any advantage of choosing one over the other? I've briefly heard both sets powered from a JL 500/5 amplifier before and didn't notice any real difference between them. If anything, the Perfects sounded a bit harsh, but I believe the tweeter attenuation was installed at -0db. I like the fact that the Alpines go from -0db to -8db for the tweeters. Any opinions for rock/industrial/electronica preference?

I'm more concerned about ease of installation - the Type R's only require about 2.4" mounting depth and the Perfects are 2.75". I'll be removing the stock buckets and I know I'll need a baffle with the Type R's.. how about a spacer? I know the Perfects will require a spacer.. 1/2" MDF should be good? However, a major advantage of the Infinity Perfect sub is the sealed box volume being able to go as low as .3 cu. ft. I'd like to keep as much space as possible in the trunk and will probably fab my own box very similar to WLaurent's v1. I'll be installing the PDX amp above the gas tank. I've got a 2005 model so I'll mount the tweeters in the factory location - high on the doors above the handle.

I'm leaning on going with the Perfect speakers & sub.. mostly for the small sealed volume of the sub than anything else. Sound clarity is more important to me than volume, so the extra rated RMS of the Alpines isn't an issue. Considering I'm putting around $1200-1500 in the system, tell me if I should save a few bucks by going with the Alpine Type R's..

 

FYI, I just ordered the IDA-X001 for $351.30 shipped from http://www.techronics.com/

Subscribing to this thread because I want to go a similar route to you...4 channel amp, sub, front speakers and haven't decided what to do for them yet. Except I think I'm going with an Alphasonik sub...

 

I used to have the Inifnity Perfect 12" in my old 1968 Camaro. A perfect subwoofer if you are looking for good low end QUALITY sound, not a crazy hard hitter, even though I could not keep my rearview mirror up with the 400wrms