Much like racing, where you have the old saying:
"Cheap, Fast, Reliable... Pick any two"
In car audio, you have:
"Cheap, Loud, Quality... Pick any two"
So... for $150, you could buy a used sub at a pawn shop or something probably, and maybe an amp in the same place.... you may be able to get it "loud", but it will sound like crap, and probably not move nearly as much air as you want (i.e. not mcuh "bass"... won't have the movement)... the amp also won't sustain it for too terribly long more than likely.
I'm not a car audio expert or anything, and frankly have no desire to be.... but i know when i hear a crap system, and so will anyone else who is forced to listen to it with you at a stoplight... My advise? Save up your money, and do it right. Buy good components, have an amp for your mids and highs, and a separate amp for the sub, properly sound-deaden the chassis, get rid of all the squeaks and rattles that the car will have, and get a box that is designed for the space within a CRX, and the exact sub that you are using. Plan on maybe having closer to $1000+ into something VERY basic, and you'll wind up with a lit better of a system that you can actually be proud of playing loudly. Realistically, if you want to impress anyone, plan on having even more than that into it.
Hate to be blunt, but its just my $0.02
