Surprisingly, my Audi S4 was super easy to install in...Battery was under the rear seat, which took easy screws to remove, and there's a pass through hole to the trunk that is easy as cake to thread through (not the center ski-pass, there's a cutout in the side). The problem is that it is a mostly sealed-off trunk, so I'm gunna go bandpass and port the box through the center pass. Currently, it's waaaaaay too quiet. I have 3 12's off 500wrms that can only barely overpower my factory rear speakers. Yeah, it's that quiet //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
I hear that newer Mercedes with the Bose setups are super tedious to install aftermarket stereos in...The ones with like 18 separately amplified speakers, requiring you to rewire each one lol. My buddy was telling me how he had to do one but all the 8 or so speakers were powered by one amp, although he didn't have the pinout diagram, so he had to test each wire lead individually for each speaker...no fun at all lol
But as far as getting loud goes, I'm pretty sure that one of the worst, if not the worst car would be an MR2...Maybe a Lotus Elise/Exige, but who in their right mind would throw anything in that?