I have a 2001 RS that came with one driver side sub under the seat. I wanted to install another sub on my passenger side. please let me know how hard is it or if its even possible.

its kinda great if you have your woman (or date) on your passenger side and she feels that pounding bass sound under her seat...you could get some great outcome ...(y'know what I mean!)

a well worth it mod I think...

 

the only thing i could think of (if you're referring to another factory sub) is to get another wiring harness and do some splicing...

i don't know if you'll get adequate power tho...