As I said above, I decided to sort the bass out on my Transit van first, as it was really poor (despite my having already installed better door speakers).
I finished the install this morning, very pleased with the result. The sound is much meatier, but not stupidly deafening. The remote is useful as it allows you to trim the response to as little or as much as you want. The trickiest part of the install was, as I suspected, splicing into the speaker output wires at the back of the head unit. There is so little space that I was only able to do the driver's side speaker (the instructions tell you to get a feed from both left and right speakers for better balance). Other than that, it was just a case of following the instructions and finding a permanent positive (battery), ignition on positive and a negative. Having said that, the Transit is far easier to work on than the Golf, because it's built like a 19th century traction engine with loads of space everywhere, accessible screws, humungous bolts and easily removable trim. Also, I'm not nearly so fussy about how the finished result looks - it's a van!

Here's a quick picture. Not much to look at, but it shows how discreet the install is. You really don't notice it unless you get down on your hands & knees to look under the seats (obviously the sub would have to be located elsewhere in the Golf). I strapped the sub to the passenger seat frame (like the Golf, my van is LHD

) to avoid drilling through the floor and to make for easy removal on selling the van. It does make the passenger seat vibrate a bit, but I won't be blasting music when I carry passengers anyway. You can also see the slab of compressed foam I fashioned from an old boot liner to cushion the sub against the frame.
I am interested to hear how you others have got on with your subs...
