We're having the same issue right now. We're at capacity and Congo would probably offset most of the MBr cost out of the options of games we'd sell.
But each time I play it, I realize how much fun it is. The rules plateau after Super Multiball, but that's not happening each game. MBr will also have that same issue.
I totally want MBr but Congo is much harder to find, shoots well, and has a ton of stuff going on. It may be a while before we pull the trigger on the lineup change.