^Good idea. I'm running an 8" (came with the car) BSW setup in my E53 and it's not enough punch. Gets too muddy if you try to push the lower frequencies to it. I much prefer 10's, and even more 12's, for near complete low end reproduction.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
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