want to add amp, sub & speakers to standard concert head unit

[KayP]

i have a new shape '04 audi a3 sport, a standard audi concert head unit with front speakers, rear speakers and a sub in the boot. i want to upgrade this system to add an amp and better sub & speakers. how do i do this?

how do i add an amp to the concert head unit?
what size sub can i put in the boot?
what size are the speakers?

i dont want to spend a lot, but still want power & quality to pump the music with the windows down.

 

[AndyMac]

You'll need to run power to the bboot for the amp, but everything else can be picked up off the feed to the Audi amp. The rear pre-outs are there as well as a "remote on" trigger. If you want to amp the fronts then you'll need to run RCA's and new speaker cable, as the fronts run off the HU. Speakers are all 6.5", here's a good right up of the upgrade:
http://www.audi-sport.net/vb/showthread.php?t=40815