I stumbled on this web site. I'm not meaning to flame anyone, but it appears to me that although you guys may have allot of experience with auto-sound (which I don't) you clearly have very limited knowledge/experience with home audio, or "high-end" (I hate that word). Some of the most respected, and expensive speaker makers use aluminum drivers.
Genesis (too expensive - went out of business) Theil - one of the most respected mfg's Klipsch etc, etc.
Have a look here... http://www.thielaudio.com/THIEL_Web/Pages/cs7_2.html
The raw (home) audio aluminum sub drivers are out there, you just have to look harder. Post this question to the www.audioasylum.com forum(s)