Before I switched to CS/Computational Mathematics, I was doing a BBA. Let me tell you, it was a waste of time. You learn jack. Classes such as introductory accountancy, albeit necessary, can easily be learned in two weeks, but you are forced to utilize the entire semester to do so. We literally spent the entire last month going over and over similar multiple choice problems because there was nothing else to learn. Now a BBA is not an MBA, but it's still a good gauge of the curriculum. Outside of the top 15-20 MBA programs, I wouldn't do it honestly.
That being said, I don't see how an MBA helps with becoming a "quant" (w/e that term really means). If by "quant" you mean some kind of researcher or analyst who lets say develops models for hedging mortgage backed securities, then how would an MBA help? An MBA is made up of courses such as management and marketing...