Rear speakers are never needed, unless you often carry rear passengers and want them to hear it better. There's no where in a cabby to stick rear speakers, the shelf gets covered when the roof's down. In my mk2 i have a decent amped component kit up front, and an 18" sub in the boot, and that sounds incredible. I'm probably doing a similar set up to what i just suggested in my cabby, just nice and simple.
Because the front speakers aren't amped you should really go for the best headunit you can afford (the blaupunkt appears to be this). The power output they state doesnt matter its the built in filters that make the differance (High pass filter is most important)
If you need any help gimme a shout, hope this helps, Andy
