The rears don’t give a massive amount of sound. They are more about providing a bit of rear fill. I have a Kombi as well, and when I ripped the rear out when resigning as insulating the kids noticed a big difference as the sound wasn’t throwing greatly from the front at the low volume it needs to be in order to hold a family conversation with background music.
Wind it up and the sound is good. With the bass control on the dash you can alter it to your desire. Tweeters give out a really good level of highs. For me, whilst the Hertz mid’s give a reasonable sound production, because it is being thrown at your ankles it doesn’t provide the crisp sound that I like from the mids higher up in the cabin.
Well worth the money though as it is a world away from the speakers that come with the van.