That is called the *** 'Audi Sound system'
As yours is the middle package your MMI I believe has a 'pre-amp' which allows the system to function slightly better than the stock.
If you upgrade your front speakers, you may get slightly better sound but dont expect to get higher volume because the MMI still be equalising the standard output.
If you want to upgrade, best to get a DSP (Digitial Sound Processor) which will manipulate the sound and trans-code it in real time to make it more flexible to use. In other words, make it sound better than the stock output. Then you can run an AMP into that DSP and then run the front speakers off it. Sounds like a lot of work but my car is getting this treatment as I've got the stock sound system with a retrofitted *** Sub only.