I had a SuperPower case which was pretty awesome back in the day, but I'm not sure do they make them anymore. You could fit almost two MBs in there and it had awesome cooling (I mean lots of fan spots and it had holes covered with nets on both sides), but as I said, I'm not sure do they make them anymore and what's the model name. If I find it, I can let you know.
E: You can also see if any Sharkoon cases fit your needs. I think they have some pretty big ones.