Hi there Jossi,
I bought my car without any radio; just the front speakers and a cover for the radio.
In my case that meant that there was NO wiring for speakers to the rear doors. I'm assuming your car will be the same.
In addition to that, you'll need a pair of adapter rings for fitting a normal speaker. You could make these yourself too: the rear doors don't really require the odd shape that is needed for the front speakers.
There are ways to thread additional wiring through the existing rubber seal. It's a fiddly job, as far as I've read about it, but certainly not impossible.
I myself 'chose' to keep the wires on the outside (although they're only visible when you open a door: my cables enter the door through one of the holes in the corner of the door).
I'd say: remove the panel from your back door and check for presence of wiring. You might be lucky and have it in place already. In that case you only need adapters+speakers.
If you'd like some more info, either search the forum (lots of info on speaker and fitting them, including links to a German A2 forum and some partial pictures). Make sure you check the 'Archive' option when searching...
Or call back here (for as long as the forum remains open...)
Cheers,
Edo
P.S. Good choice for a head-unit! I considered it too, but feared if lacked some features in the display and sound-setup department. But technically a very sound unit!
--
(2003 Silver 1.4 Tdi Exclusive(SE), 95bhp/235Nm chiptuned by ABT, black interior, sport seats, heated mirrors, TomTom3 PDA Satnav, JVC KD-SH909RB cd-receiver, Infinity Kappa 63.1 + Vifa on-dash tweeters, 12" Subwoofer on 300w Amp)
