The "standard" DuoProp (the DP-S) is available with engines all the way up to 420 hp 496's, so you'll be fine at the numbers you're talking about. For really big power (up to 600 hp) you want the DP-X.
By the way - The DP-S is a silver-colored drive with through-prop exhaust. I'm not as familiar with the older style white units with bullet tailcones on the props. You can also check www.penta.volvo.se for more information.