I am currently running a Diamond Audio 10 powered by an Alpine M450. VERY nice. Roughly 400 rms and it rumbles. I find the Alpines to be strong and reliable. Don't think you could go wrong with either.

That L7 must shake your whole car!

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2004 BMW X5 3.0i - Mine
2011 BMW 328i xDrive - Hers
2002 BMW 325xi - waiting for a new owner