I'll tell you what I (tried to) tell my Home Theater clients. Don't worry as much about your amps going in (for full range) and spend the bulk of your budget on speakers. At the end of the day you don't 'listen' to an amp, you 'listen' to your speakers. You can have $2000 worth of amps driving $250 worth of speakers and you'll NEVER be happy. :nomore:
I mentioned (for full range) because the ONE place you need to spend decent money on is your sub amp. Sub boxes, especially for trucks can be found at just about any pawn shop you go to. You don't need a 2000w or even a 1000w amp for your sub(s) as long as you have one that can handle high current. Take a decent 500w sub amp and it'll be more than enough (unless you like to ride around rattling your gas cap and license plate).
Eons ago I ran ADS Power Plates, a 40, 80 and 120 in a regular cab truck and it was all anyone ever needed. These days you'd never get away with that though, I mean NEVER! Those old ADS amps if it was rated 2x40, it would do that all day, every day, into 8ohms, and at 2ohms it was more like 2x120. In theory.... a unlimited current amp should indeed double it's power output with every halving of the ohm load, so yes,
40@8,
80@4,
160@2, and even
320@1. In *reality* however most amplifiers simply do not have the current to drive the output stages to such levels. (Even if the output transistors were capable of sustaining the load(s) and more importantly could dissipate the heat.)
The other side of that coin is in theory a speaker needs double the power for every 3dB of spl output over it's nominal rating. IOW's... Take a speaker at 86dB~1watt(again in theory),
89@2,
92@4,
95@8,
98@16,
101@32, etc.
Take a good speaker that is capable of getting really loud, and can take the power, and you start to see how they'll suck the life out of an amp in a hurry. That being said, most music is listened to at under 100dB, with most power requirements being well under 20 watts, and is why you see so many multi-channel amps in the 40 watt per channel range.
Sub amps however are a different story. Take a good dual voice coil sub, two 2ohm coils running in parallel and you're presenting a 1ohm load to the amp. That's almost like a dead short!

(well not really... but it'll kill a home amp in a few seconds) Can you get away with a 500 watt sub amp? Absolutely!!! (I did it with a 2x60 into the low end, competition 12's and could drive them into the low 120's all day long for YEARS!) Then again.... they don't make um' like they used to.
In my kids 4Runner we went with Pioneer component speakers in the front doors, coaxial's in the rears and even with 'matting' all 4 doors (which made is sound a LOT better) I wouldn't do that route again. Not exactly the sound I was looking for.
The head is Alpine, as well as all Alpine X power amps. Picked up a Kicker L7 12" (port loaded) in a 3.5 cubic foot box at a pawn shop for only $120.

It could use a much bigger amp actually, and it REALLY needs a sealed box. He likes it though, and has actually learned to play around with stuffing the port to clean it up. For me it's way too muddy and floppy. Although most everything HE listens to is dubstep (that he mixes) and it's just what he goes for. Go figure......
