I know there are a lot of varying opinions on here regarding the level of sound quality in the Model S (perceived or otherwise). The two popular upgrade routes I've seen are as follows. There is the premium sound option from Tesla that adds additional speakers, one of which an 8" sub ($3K now maybe?). Then I know that others on here have turned to Reus for a complete audio package (I've seen that price in the $2500-$5000 range). Absolutely no offense to those who went either of those two routes, but they weren't for me. I just needed a professional subwoofer addition to compliment the existing basic audio system. While I was slightly impressed with the 10" pre-loaded box from NVX, I was not impressed with the $700 price tag for the sub/enclosure alone. I do have moderate experience in car audio, both wiring and custom enclosures. So on that vein, I set out to design something that could meet my needs at a reasonable cost. Teslatap.com has a superb and what I would consider a definitive installation guide on adding a subwoofer to the Model S. Using that as a starting point, I set out to create a custom enclosure made of fiberglass and MDF that fit in the passenger side fender alcove. Then loaded that with a 2ohm JL Audio 10W1v3-2 10" sub and powered it with the 300watt NVX MVPA1. I took the Teslatap.com guide to AAP here in Columbus and worked with them to help me bring it all together by having them do did the actual wiring and amp install, while I installed the enclosure afterwards. The result is something I would consider well worth the time and effort. Materials and installation came in under $600 total, although I did not put a dollar amount on my time to fabricate the enclosure (4-6hrs max). My source material is primarily 320kbps MP3 files with a smattered mix of slightly lower bitrate material along side lossless FLAC files. No radio, internet or otherwise, ever. Bottom line, everything sounds better at every volume. Slight tweaking can still be had from the limited bass-band equalizer when necessary. And even at 10", with the trunk area opening into the passenger space, the sub can hit very hard when needed. It's not going to win any competitions but it is going to make all my music sound very good. If you are in the area, I'd be happy to demo it for you. Otherwise, check out the end results in terrible camera-phone quality. I also was toying with adding a cloth cover to the front for discretion and protection. Comments are welcome, although I like the cover even though I can still see the seam.