What year GTI do you have and what radio system? I'm lucky, I have an 05 (well, reg 04 but it's 05 model...) and the MFD2 with 10 speakers and I think it's great. I understand that the 06 cars had 2 of the speakers cut out.
VW do a sound upgrade pack at a reasonable price that includes 10 speakers and an amp, might be worth investigating?