Wouldn't the end result still be the same? The 3 speed and 4 speed's final ratio is 1:1, so the rpms wouldn't be any different when in top gear. All you would be gaining is an extra gear 'in the middle'. Unless I read your post wrong...
Married? Have kids? How about a girlfriend? What happens in the middle is often times the most fun of the entire endeavor, even if the end result is the same. LOL. Couldn't help but go there.
