First of all, I took a chance with this amp, as there were not any reviews that I saw for it. And I've never met a class D amp that I've liked before, besides sub duties. I've had Kicker, Arc Audio and RF class D before. All told in the last few years I've had 10-15 amps. From Massive to Audio System and more than I car to name, or tell my wife. No truly high end stuff, but the Audio System Twisters being my favorite. The car it is in is a Scion FRS, so space and weight is at a premium an I wanted to keep the use of all the space I have. I wanted a 5 channel that I could fit under the passenger seat. Also did not want to shell out the money for th JL.
Install: Probably the he worst instal I've put an amp through to date. The amp is only 2" tall, but there is not a lot of room under the seat in this car. I had to take out the foam under the carpet and raise the back of the seat a tad bit to fit it under there. So we end up with maybe 1/4" of room between he seat and amp. Probably not that much.
And I've had a few multi hour listening sessions with no stop in the music. It gets hot, no doubt, but no shut off yet.
Gear: I'm running a 80prs, Focal krx2 mids, Dynaudio md130 tweeters, and an Alto Mobile Falstaff 12" sub.
Features: Of note on this amp is the ability to run a 2way+ sub with the on board crossovers. Think this is new for the PDX line. Other than that I think it is pretty similar to the other PDF amps. Uses plugs for all hook ups, which I like. Has a bright ass blue light on top of it, which I do not like.
Power: The birthsheet says right at 120x4 and 600 watts for the sub. Can't recall exact right now.
Sound: First of all, it is dead quiet. No hiss, wine, clicks, turn on bumps, nothing. Which is a good thing. Second, it is very clear. Crystal clear. With the drivers I'm using, you can reach truly ear damaging volume with no audible distortion, at least to my ears.
As far as coloration, I can't hear anything that would make you say class d. I think it does a very good job of just amplifying the signal.
Now to compare it to the best sounding amps I've had, the twisters. I spent the better part of a year with those amps and there is just something about them. That Italian-ness maybe? I would have to give them a slight edge over the alpine. BUT, for the size and price of the Alpine and the space I had to work with, the Alpine pdx-v9 is a very solid choice.