Duke-
I'm sure you'll get a variety of options here, so I'll let others that have fold down bench seats and other options describe those. However, I have heard that the more permanently mounted fold down bench seats in the rear make it harder to access the bilge well, and everything else behind them and under the transom.
What I have is simply a 120 quart cooler with a padded top. This works great for a seat while doing its primary job as a cooler. The factory ice-box under the helm seat is notoriously small and difficult to use (often replaced with a shelf/cabinet at no additional charge). So one must have the cooler anyway unless going for an electric refrigerator such as a Norcold, which is a big battery consuming convenience and about $900, unless you install it yourself for about $600.
The large cooler can also be used as a "double insulated" unit in real hot weather, where a smaller cooler can be put inside it, giving extra insulation, and the extra left over space can then be used either as dry storage or extra single insulated cold storage with ice in it.
A simple adaption of this would be to use two smaller coolers instead of one, so as to have two smaller seats that can be moved about as needed. When a cooler is placed along side the gunnel, parallel with the longitudinal axis of the boat, it also serves as a step when entering the boat, but might require some shimming to keep it sitting flat on the slightly angled up sides of the floor/hull.
Like anchoring systems, there are a lot of alternatives here, and the best one depends on your individual needs. Joe.