I'm not really into modifying as I like my Gti's pretty much standard, call me an old fart. The only thing I've modified on my 8v mk2 is the stereo and speakers. I didn't do any research but went for some pretty standard alpine speakers (front and back) and was given a pretty dated looking sub and amp by my girlfriend (unwanted now from her raving days!) and the sound quality is absolutely astonishing!

I'm a keen musician with a good ear for music and sound production and I guess I just got plain lucky on this setup! I think the speakers were about £80 for the lot and the sub n amp were free...how lucky am I!!!
