Previous owner of mine had the Parcelshelf cut and a small 8inch sub put into it. I was moaning about it one here a couple of months ago saying it was crap. I have since noticed the filter on the Amp was set to High Pass, one quick flick later and it's improved massively!
Much much better than just the speakers on there own, I'm no boy racer, but there are times when I like to listen to music and find it helps a lot. Just a shame the Professional outfit that installed it should have done a better job! The cloth over the top of it isnt the best fit!