Can Concert Stereo run another sub?

Hi guys,

I have the Audi Concert Stereo in my avant which seems to be pretty capable but I want to set up a sub in the spare wheel enclosure. Will the headunit be able to do this? There's a smaller sub in the boot already (not sure if option or standard) so wondered if I would have to take this out or whether I could even use the same wiring and add the power cable?

Any help appreciated, and if anyone has done a spare wheel install it would be cool to see some pics.

Thanks in advance

Bradley