My friend had this installed in his car by Halfords after he bought it from them a few months ago.
The setup was very, very lengthy. I am not too sure whether this was because the subwoofer was awful to set up or whether the Halfords employee was just completely incompetent. However, as the employee is supposedly very experienced at installing such devices, I assume the 3 hours we were waiting for it to be installed were because of the subwoofer. The employee did mention some issues he had with the subwoofer but obviously we didn't really care once it was working.
Now to performance, we were told to keep the subwoofer on low for the first few days to break it in a bit. However even with it on about 20-25% of its full power the bass was incredibly deep. Especially as I was in the back seat ont he way back and therefore right next to the speaker!
About a week later he had it on full power and to give you an idea of how powerful this subwoofer is. I heard him coming when I was in the back of my house, with the windows and doors shut, when he was still halfway down the road. This wasn't even on full power. If the loudness is what you are after, then these are perfect for you.
Inevitably, I was in the back seat again this time and I really do not recommend being so close when you have them on full. The front seats do not really SUFFER from the speakers but the people in the back seat merely hear bass directly into their ears. If you are ever in the same situation as me, you will miss your sense fo hearing for a couple of hours afterwards!