Hence my concern. I have no problem switching to a 4 ohm driver provided I maintain the current output. I did a lot of experimenting in my previous vehicle including MB Quart comps, which I found to be too bright. The setup that I removed prior to trading the car included CDT EF61 comps, a single 12" Elemental Designs 13Ov2 (sealed), and an Alpine MRV-F545 to push it all. The comps were getting 125 rms per, and the sub was getting 500 rms. I am debating wether or not to install all of that equipment in the X5. Judging from my eyeball measurements I would say I have a 50/50 chance of getting my CDT's in the stock housings. The tweeters fit perfectly.

I really think the stock system gets loud enough for my taste. I would consider replacing all stock speakers and retaining the stock amp, but I want to maintain the current output. I will eventually replace my 12 with a single sub in one of the "stealth" spots.

Sorry for the long post...

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