Prior to duct taping a pair of sunfire mini subs to front and back your head, I would try another headphone amp. You might try to find a dealer that handles Can gear, and also listen to a pair of Grado RS-1's. I have never felt like I was missing any sensual bass with my Grado's.
Can I use Headphones AND a Subwoofer?
Has anyone done this before. I have the Senn HD650s which, I don't think are considered closed. They're not like the AKG K100s either though. I'm missing the sensual bass I used to have with my speaker system and was wondering if this would be a fruitful pursuit. Any thoughts besides, "Your Crazy!"?