i've also got a 4.150 PDX bridged, running just my fronts. it's tuned so that each side is getting just over 250wrms at like 80% volume.. just before any risk of clipping comes in. it's running MBQuart reference splits.
I'd go the 4.150 rather than the 2.150 because, as was said earlier, it's a couple hundred more and you get twice the power and more tuning options if you go active.

If you head to Alberts Car Sterio in Joondalup (a hike i know) and say you KNOW you can get the price there and what can they do you for (flash some cash), you WILL get the best price in town.

I can say that Alpine PDX amps are quality, will last forever, are small and powerfull and look good! and because Alpine is sold like it's going out of fashion, you can get a good price on them if you haggle, specially buying 2 at once (if you do)

__________________
[COLOR="Blue"]"Your car positioning and awareness is f*ing bang on. And like, every single time.
In terms of getting that close to the bollards, Ive only been with one other person that can drive like that" –Franz[/COLOR]
[SIGPIC][/SIGPIC]