Bmax is supposed to be good thru 800 or so.
Max is a tough unit, but that's a lot of power for stock Merc sized gears. They say their new billet drive has been tested with 1500 horses. You're sort of on your own though since its a new drive.
Konrad is coming out with a shiftable Bravo replacement. Their stuff is beefy. They will also fit their proven nonshifting drive on an extension box that houses the tranny. I like that idea but its pricey.