Im pretty new to car audio. I have a 1000w alpine amp with no sub. I would probably like to have a 150w rms sub, can i use my alpine amp to run it or does the size difference make it not a good idea?
So right now I should either buy a small sub / a small amp - sub / or just a larger sub??

 

you dont need a bigger sub... but if you dont wanna waste most of the amp then aim for something with higher power handling, more power in the sub means more mounting depth usually, but there are 10" subs that handle 100w and 10" subs that handle 10,000w (albiet for a very short time) but either way keep the amp, if you get a low power sub just keep the amp turned down...