here's a few ideas
Let me start out by saying that you own a very beautiful piece of equiptment there. I owned a BMW once (a salvage title 1990 325i turbo) and it was probably the fastest (0-60 in 6.2 seconds!) and most responsive vehicle I've ever owned.
I know that a few companies make small bass drivers like you're looking for. JL Audio makes a 6" or 6.5" and so does Digital Designs. Both are great drivers (definatly superior to the Fosgate) and will fit the application of .1 to .3 that you mentioned.
I've heard all three (Fosgate, JL, and DD). The Fosgate and JL are in the same price range, and even though the price difference between the JL and the DD is pretty substantial (The JL retails for about $85-$100 and the DD for about $150), they both sound very similar to me. The fosgate sounds okay, but it's not as punchy as the other two.
The only problem with a small driver of this sort is the low end frequency response you would get with a 10" or 12" versus a 6-6.5" sub is compromised because of the small cone size. To put it simply, you're probably not going to hear anything below 60 hz with either of these subs, no matter how either company rates their product. But, depending on the music you listen to, you might not need that low end anyway.
My suggestion to you would be to check out both drivers I mentioned before going with the Fosgate. Who knows......you might like the Fosgate better, but I'd almost guarantee you'll like one of those better.
BTW....You might want to check out Cadence's Z6000 amp. It's a six channel amp with 75w x 6 RMS @ 4ohms, and the power doubles at 2 ohms. The THD is 0.044%, and you can run the channels in pairs so that some are 2 ohm and others are 4. This would probably run your entire system pretty efficiently, not to mention the Cadence amps look cool as hell!
Hope I've helped you at least a little!
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