On the subject of BOSE... I have a US market 320 (R170) that has the Bose sub-woofers in the rear as well as the telephone/SOS system and CD changer in the boot. The head unit is a cassette player, which is kind of useless these days. The telephone system is analog; also a bit useless. I've seen the UK market had an in-dash CD player, model FM2910 part no A 170 820 03 86, which I have found on eBay for a reasonable price which I would like to have in stead of the current cassette player. My concern though, is will it work with the Bose sub system? I an under the impression that the rear channel drives the Bose amp and subs, but the audio settings on the head unit has only bass, treble and balance, no fade (front to rear). Any advice is helpful. If you have a UK or Euro market SLK with this head unit AND the Bose sub-woofers, please let me know. Please... No speculators. If you don't know FOR SURE, please don't reply. Thanks.
UPDATE: I got an in-dash CD player from the UK, Model 2199, MB part No. A 170 820 01 86. Popped it in and it works fine. FM stations... No problem. I didn't seem to be able to tune into any AM stations on any of the AM bands, but for the most part I don't listen to AM so it is not an issue with me. This unit will not, however, play copied CD's, you must use originals. That was a bit disappointing, but I knew this was a possibility when I bought it. The Bose subs work fine since they are run through the front channel. The unit still displays the fader (front/back) audio adjustment even though there is nothing hooked up to the rear channel, but I just set it 100% to the front. I'm happy with it since the cassette player was obsolete.
Yes, the FM channel issue is a concern. I've had conflicting information on that but the seller says it will work with US channels just fine. My current head unit FM range is 87.5 - 107.5MHz. The Audio 10 CD player is 87.5 - 108.0MHz. I will have to do some more research on that.
As far as the Bose system goes, the door speakers and rear subs are run together on an integrated amp that splits the low frequencies for the subs in the rear bulkhead. The only input is the front channel, LF-, LF+, RF-, RF+, leaving the rear channel on the head unit not hooked up to anything, according to the wiring diagram, so it will work fine in that regard.
The unit I am looking at is reasonably priced so I may just go for it and keep my fingers crossed. I will up date my results, of course.
I have a UK 320 with Bose and I can confirm that my HU (also an FM2910) only has bass, treble and balance and NO fade. I thought this was odd as well (not had the car long) but, once I had thought about it, the rear speakers are just subs at the end of the day and don't need 'fade'.
I was very annoyed that it only had a single CD option too and quickly looked in to adding an Ipod, connected to the antenna so that it plays on FM. However, the better half said she would buy me a lovely little Pioneer HU for my birthday! So, yesterday I fitted it and WOW! The sound is phenomenal! With the Bose amp AND the MOSFET in the HU working together, it is incredible. Plus, to boot, I have Parrot Bluetooth built in, rear USB's so that I can hide the Ipod wiring, DAB, single CD Mp3 player, SD............ (Pioneer DEH-X8500DAB for anyone that might be interested).
Bose was a very expensive option in the uk, and not worth the money. I spent some time last year researching how to make the SLK "sing". I ended up with a fairly good Sony HU and a set of Focal door speakers. I think there is a built in amp which is being used as there is no way the Sony could output the sound levels available. The Focal speakers (plus Dynamat and a bit of EQ) sound very similar to my B&W CDM1NT speakers at home. I have not bothered with a sub yet. I am enjoying the clean Focal sound to much to want to ruin it with overblown bass.