I'm going to go by where gear is for sale all of the time. I can tell you by the dealers available that Texas, per capita has to be one of the worst. Houston is the largest city in Texas, the 4th largest in the US, and has about exactly ONE high end audio store. I say California, New York and Florida (which is really an extension of New York) probably have the most audiophiles per capita.
Followed by states where it's very cold for a long time, Utah, Colorado, Illinois, and Minnisota.