I have a very large room, and at this point I still use small on everything and 80hz crossover on my Denon. I played around with setting my 80's to large and using LFE+Mains to see if that would help with the nulls/peaks. I did not see much of a difference if any.

Some day I hope to add additional subs on the other 3 walls. \:\)

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85