@pepsiman: From what I can tell, they had some sort of contractual work involving the graphics. Enough to score a mention in the credits anyway. It's probably about as deep as their association with Smash Bros Brawl, but it jumped out at me when I was reading their Wikipedia entry.
I'd love to hear more about Soma Bringer. If Monolith really hits it out of the park with this "X" game, there'll probably be a lot more interest in their past projects. Maybe Nintendo could remaster the two Baten Kaitoses in HD once they're done with Wind Waker? A guy can dream, I guess.