I haven't gutted the trunk area of my X for a few months, but if we're talking about the same thing and making an enclosure similar to the size of BSW's, then you could make your own enclosure and put it on either side since you're ditching the factory setup. I removed the factory amp and rewired all 14 speakers locations in my 740iL...it was hell, but I got it.

You mentioned that you're planning on keeping the factory deck so you can use the steering wheel stereo controls, so I don't know how you plan on being able to do that, unless I missed something. I'm not sure how the tuner works, if it's independant or intergrated into the stock deck since I'm bone stock in the X and completely custom in the 7.

The electrical system in BMW's have and always will be hell, but I haven't had any problems in my 7. I run a 1500watt monoblock MTX 81000D amp running a single DVC RE Audio 12" in a huge box, no cap, and it runs w/o a problem. It's convenient that the battery is located in the back, so your amp will love the short current path of power. I'd just make sure to use screen 7 (I think) on the OBC and monitor the battery voltage if you suspect your system is giving you gremlins after you get it up and running. I still run the factory BMW battery in the X, but the 7 had a Duralast (Autozone) 69D (I think) battery...similar CCA and size, longer warranty and only cost like $90.

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