I need to send my out-of-state college freshman son a powered subwoofer for his dorm room. He's keeping up awesome grades

He has a set of powered monitors that struggle with low frequencies. Obviously we're not talking about audiophile listening, just bass-heavy young people stuff

Don't need to worry about HT or gaming or anything like that. Just want to extend and fill in the bottom end of the music with something that can take a beating.
I'm hoping to keep it around $100. Are the Dayton units at parts-express good candidates, or are they geared mainly for home theater use?
I have the ability to build something from scratch, but factoring in shipping costs it might not make financial sense.
Any suggestions would be appreciated!
BK