I have no experience, but from a quick browse in the "shop" section £3 to £5k is going to be a challenge in that dealer for a system. They don't seem to have much mid range gear.
As you said, they look a bit more high end, so personally I would give them a call, or drop in, and discuss your requirements with them, and see what they suggest.

As for taking your own music, you may not need to if they can stream, but make sure you have a robust play list.