Columbus upgrade possibilities

I've had my Columbus fitted to my Octavia vRS for about 6 months now and think it's a great unit. However, I think it should sound better than it does. I believe that, as it came from a Superb originally, there is something in the coding that should change the sound to make it better suited to the Octavia. Can someone confirm this please? (and is there anyone in the Cheltenham/Gloucester/Worcester area who has VCDS who could help?)

Secondly, what options do I have in terms of fitting an amp? Again, I believe that the outputs are 'high level' as it stands which limits the choice of amps, but that the coding can be changed to make them 'low level' outputs. I am not looking to fit a sub (unless one can be fitted under a seat), but just want to improve the quality of sound that I currently get.

I will change the standard speakers too whilst I am at it as I guess they're part of the problem.

Thanks in advance,