No doubt that premium fuel is the best, but is it worth it? Regular fuel is about 2.50 per gallon currently.
Premium is 3.25 in my area. Lets be conservative and say premium is only .50 per gallon more than regular. With a 20 gallon tank you would save 10$ per tank by using regular. If you spent that 10$ on the 87 octane, you would net way more than the 20 miles of extra range that you mentioned. Is the 20 extra miles per tank and the extra 7-10 HP worth the extra cost of premium fuel?
ETA: Consider the fact that overwhelming majority of folks don't buy premium, so the premium fuel at most gas stations is probably older and has more condensation and oxidation in the storage tanks than the regularly used 87 fuel.