I have a few questions/ideas thought I would put them all in one place so if you can offer any advice on them please reply!

I have the factory fit concert tape deck.

1. Has anyone any experience of keeping this head unit, converting the front speaker output to low level and then fitting an aftermarket amp for all 4 channels with uprated speakers? (I have some 13cm Pioneer components for the front, 17cm Pioneer components for the rear and a 4 channel Alpine 3555 amp I can use).

If so, what was the quality like from the head unit?

2. My plan is something like the xcarlink for ipod into the cd changer input at the rear of the concert unit. Does this work well with the Audi concert unit?

3. Also, if the rear speakers are upgraded, is the factory amp powerful
enough to power them, or will they just sound as dull and poor as the factory speakers?

Cheers.
Stu.