I had an MIJ System, drove up to B'ham from Portsmouth, used them on my last car, great quality, decent service.
http://www.350z-uk.com/topic/78825-grundys-eleanors-sexy-new-wheel-page-24/
You'll see the setup, and sound clips in the above link.
Did you get that quote in writing? Or just over the phone.
As I got a quote via email. Was around £400-600, can't remember exact. But basically when I got there, they didn't realise twin system etc, and said it would be around £900.
But since I had the email, they couldn't charge me any more as they'd already quoted me
Little tip there.