I've been lurking here quite a while and just wanted to thank everyone here for all of their (unknown to them) assistance with all of my 2001 slk320 related needs over the past year and a half. I actually did this install on the quick and spent about...475$ total. Some of the tips provided by the other threads on installing were extremely helpful. Thank you so much.
$100 Pioneer MVHX560BT digital media receiver headunit (NO CD!) Old model, Out of Stock on Amazon.
$10 Metra Harness
$5 Metra Antenna adapter
$10 USB and AUX jack extender
$75 JBL GX600C 6 1/2" components
$120 Rockford Fosgate Prime R300X4 amplifier.
$90 6.5 inch earth quake subs
10$ Couple of sheets of Noico deadener. (bought an entire large box for 35, only used 6 sheets)
10$ 50 Amp breaker on EBAY.
30$ Additional wiring
Head unit install with the adapter was pretty much a no brainer. Offhand I can't remember if I had to swap the constant/keyed power leads on this harness or not. I'm thinking I didn't.
Power for the amplifier was sent down through the relay/fuse box to the amplifier mounted behind the rear seat. It does take up a small amount of room, but I never have anyone over 6 foot or so in my passenger side anyhow. I wasn't worried about losing an inch or two of travel. The USB and aux wires were relocated to the middle console in place of what used to be the cigarette lighter. (Though I'd recommend the smaller 6 feet lead, the 12 foot was way too long and HAS given me issues with connection. It will be replaced soon). Noico sheets were used opposite the mounting holes in the doors as well a decent section under the matting/plastic section of the doors. It helped to create a bit more thunk when the doors close as well. All new wiring was run to the speakers from the amp, the pull throughs for the doors weren't too bad, but I recommend opening the doors ALL the way up, it will help with the passing of the wires immensely. Microphone was routed to the original location but needed a muff to make it usable at in town speeds with the top down. At highway speeds. LOL, Ain't happening. I wasn't fond of the idea of a mic sticking out of some place obvious so I'll deal with it.
I've heard some talk about the earthquake shallow subs being a tab anemic, and I agree, but only in the much lower end of the volume spectrum. I have mine set at the head unit to let anything under 200Hz go through on a flat EQ and the amp passthrough set to though. The components up front are using an 80hz crossover point, also from the head unit. It's not going to win any competitions, but if I want the guy 2 cars ahead of me to know what I'm listening to that's not going to be a problem either.
*edit* will have to add more to this post later. Need to get to work, sorry!