I haven't owned a high-end audio business, but I have been an audio salesman several times. I live in Seattle, but have spent time in southern Oregon. I don't mean to discourage you, but my immediate reaction is that you will have a tough time running a successful high-end business there. The population is quite low, many of the people earn modest incomes, and the economy -- while not depressed -- is certainly not robust. I have a very close friend who bought a business a year ago in Eugene, and he has just declared bankruptcy because the overall economic situation for small businesses is not very good right now.
I think you will find that many of the audio-only stores are having a tough time making ends meet. The ones who are succeeding have generally been forced to become a combination audio / home theater business, with most of their cash flow coming from HT. In southern Oregon, I have real doubts that you will find enough clientele to succeed. You could, of course, have a "clicks and mortar" business, where you rely on Internet business as well as walk-in sales and home installations.
You would be well advised, it seems to me, to call the few high-end dealers in the Portland and Eugene areas (there are several in Portland, and one in Eugene if my memory is correct). They can give you very specific advice about lines to carry, start-up and operating costs, etc. You should probably have enough cash to live on and pay bills for 6-12 months. And, of course, you should develop a sound business plan, which may require the services of a pro, although there is a good software application called "BizPlan Pro" that will generate a plan that is acceptable to banks (if you are seeking financing).
I don't mean to sound unduly pessimistic in my response to you, but given the general uncertainty of the economy, even in areas where the economy is strong, you may be trying to launch your endeavor at a bad time. Talk to other dealers, however, and solicit their honest input. Before you invest any money, do a LOT of research and listen to the advice you get.