The first trhing I ould do is load up the car with sound deadening (e.g. dynamat or brownbread). The mk5 interior is made out of really cheap hard plastics (nowhere near as good as the mk4!) and once you crank up the volume, it rattles like crazy. Also, the general road noise is really loud on these cars so reducing that will make the standard speakers sound better anyway.
Yeah, this is true and good in practice but I won't be ripping out any of the plastics or adding any sound dead panels. Not something I'd really be comfortable doing and I don't want to take out anything like that or replace it, purely so I can leave everything as OEM and untouched as poss if I can.
When I sell, I'll replace the OEM speakers if indeed I change them, again just for continuity and originality.
So Hertz components are the way to go? I'll do some Google'ing.
I might even get just a small sub to give a little punch if the built in woofers on the speakers are a little under powered for that?