I put the MB Quart seperates in my car a few days ago(Reference RCE216). Big sound improvement. The crossovers are so big I couldn't find a place to mount them. They look nice but I didn't want to leave them visible. I ended up mounting them in the door behind the 6.5" woofer. I drilled a couple holes into the reinforcing bar inside the door then I ran a beed of silicone along the back of the crossover and screwed the crossover to the reiforcing bar. I am a little wooried that the vibration will cause a problem with the crossover but so far so good.

I can e mail a photo if anyone wants to see how I installed it.

 

Why don't you post a photo?

 

Move the crossovers, the door is filled with moisture and you are on the wrong side of the vapour barrier. In no time flat this will lead to a failure of the crossover and possible damage to the speakers. Good idea, just forgot that one little thing called mother nature.