Re:. . . . The age old problem . . .
Yeah, car stereos are great for one thing mainly. I listen to stuff like Audioslave, Rage against the machine, Linkin Park, etc in the car. That kind of stuff sounds great cranked up with the windows down driving fast.
I added a new head unit, speakers, sub, crossovers, amps for rocking out while I drive. I never listen to mixes in my car though, sounds like crap. I don't play music like that personally. I do find that my wife's minivan is very telling.
I guess the point I'm trying to get to is that a good studio with a neutral room reponse is going to sound different than a Aiwa boombox in a concrete basement...as is a car stereo optimized for one sound in a certain car, yada yada.
I vote you ditch the sub and get some good cans to refernce the bass. It's way cheaper than dealing with the room problems you most likely have. I am not a big fan of the auralex stuff. You would problay be better served with the OC 703 stuff and some DIY panels set-up properly. The Auralex treatments I have generally seen only take care of flutter echo which seems like an improvement in the room, but actually only treats a narrow frequency band (2.75Khz to 7Khz). This can affect reverb use in the mix, and cause scouped mids. I have been mixing in my room for about 2 years, and it's an ever evolving project for sure. I ruined many mixes of good songs while learning the room. I add new treatments as I go.