Stani, HU is important but not that much. I use an old Silvercrest shi..sh that can only play music trough AUX. 
The most important is the front line, the rear is more for a richer and balanced sound.
You definitely!!! need to go for a set of component speakers. I got Pioneer TSE-17ci. Fabulous sound!
Installed:
I also use an active subwoofer to give it a bit of punch
This baby is now under the pass seat:
And this is where the music comes from:
The rear line is pretty much standard 6/9 speakers.../ to be replaced by Pioneer TSE-13ci at some stage though...
You can go for the same or similar set up and you'd be more than please unless you look for a 1000+ W sound, which I think is unnecessary for a day runner.
Ah, and another important point: sound deadening for the front doors and boot. Best option I believe is
Secondskin Damplifier Pro Kit - fantastic results!!!
(Y)(Y)(Y)
