When listing fare classes, is "Q" the next highest above "N"? In FewMiles' list "N" is listed as 8th. tier economy and "Q" as 6th. tier. Is there a 7th.?

I'm trying to do a cost-benefit analysis of upping a 10K+ "L" flight in the New Year to "Q" for purposes of the latest promo. (The last time I had to do this was to get an AAVacations "S" fare up to "N" to use a mileage upgrade - the cost was around $100 per ticket, which was worth it at the time for a flight to Hawaii.) I like to be armed with the facts before calling AA and someone here usually has the answer.