Sub only?

[gamerman4]

I was wondering if you can just buy a subwoofer for a PC w/o the speakers because I already got speakers. Preferrably not too expensive ($20~$40)

 

[vortmax]

if you're sound card as a coax LFE output channel, then yes. Any powered home theater sub would plug into that and run fine. The other option is to put a cross over between the sound card and speakers. That will strip the frequencies below a set point and send them to the sub.