@Countzero, not neccesarily. The speakers in mk4 Golfs and I think later models as well far outperform the headunit fitted and it’s recommended to drivers of those models to upgrade the headunit alone so it is supplying sufficient power. I’m running a 4x55w Alpine unit and it’s superb.
OP, your best bet is gonna be to ask the lads on Briskoda.net or just have a browse of the site. I’m sure you’ll find the answers you need!