I used to live in Boston, and there was ONE high end audio store downtown, and a few in the suburbs.
Lechmere, CircuitCity, BestBuy were selling some high end stuff as well and as we know they are all gone. (BestBuy is hanging on by a thread)
I think today's landscape is similar, very few high end shops. Yes, if you live in a city of over 2 million, you will find probably 5-10 stores. But it will exponentially diminish with size.