My opinion, you don't need nearly so many watts, and I'd pick a quality lower watt amp along with a smaller woofer, 8-10" is plenty.
I have a G1 so it's not apples to apples, but I picked up a used 250w (RMS) kicker mono amp from eBay for about $50, a Planet Audio 8" sub for around $25 on Amazon, and used some scrap wood to slap together a box that tucked away in some of the deadspace in the car, so the sub wasn't taking up any of my valuable cargo space or migrating around while taking corners a little too fast. I keep the volume quite low - the sub is only there to fill in the frequencies which the door speakers simply don't produce - but even with "just" 250 watts RMS, it could very cleanly damage my hearing, and I cringe at the thought of subjecting everything in the IMA compartment to that level of vibration.
I picked this amp specifically because it was one of the least expensive class D amps I could find which wasn't Chinese garbage. As I understand it, A/B amps have a much heavier electrical load and dump a lot more heat.
The entire box took less than an hour to make using hand-held power tools, not including time for glue to dry, and it's a rather complex shape because of the space it had to fit into. I opted for a sealed box (instead of ported), which to my (admittedly uneducated) understanding is a bit less efficient in terms of db/w, but is easier to make sound good.
If I had to pick from some of your premade options, it would be between the Kicker and Pioneer, I think.