I'm puzzled by your statement that the golden rooms are long and narrow. this site
Home Theater Room Dimension Formulas & Calculator has a chart showing the three Sepmeyer ratios. The longest room is 2.33 times the ceiling height. If your ceiling is the usual 8 feet or so, that means the room is only 19 feet long.
The least-squarish room in the list is only 1.4 times as long as it is wide. I wouldn't describe that as long and narrow.
And, unless you are buying some uber-expensive system for ultra-critical listening, I wouldn't get too worked up about it. Go to the site in my link and put in your ceiling height, and try out several different room widths. Look at the three room length results and see what best matches what you've got, and go for it!
--hope that helps.