Room simulation in reverb is a dead end. Give it a bit of thought... To reproduce all the discrete echoes of a room, their phase difference, how they bounce back and forth between walls, is a hopeless task. All the good reverb designs are based on what sounds good rather than realistic simulation.
@whale-av is right about doubling a nice sounding verb, changing the settings slightly on each and feeding them into each other. But if you are assuming your sound source and receptor to be at the center of the room, you don't need 4 channels, as left distance = right distance, and front distance = back distance. Indeed if you are assuming a quadratic room with speaker and mic at the exact center you only need one channel!
I find Puckette's algorithm to be very efficient and convincing (rev2~ and rev3~) compared to freeverb which is based on a very arcane algorithm (Schroeder back in the 60ties). Both [rev2~] and [rev3~] have 4 outlets so they can be used for quad mixing, What puckette's algorithm is missing maybe is the allpass smudge of the freeverb/schroeder models...
See also this video on reverb design which goes through the history of reverb algorithms: