Dave,
I've got a 2004 170DC we bought a few month's ago, so I'm far from and expert. We've put about 25 hours on the boat so far, and just love it. We've got the Yamaha 75hp 4 stroke, and it's quiet, with plenty of power. 8-10 hours of cruising, trolling and responding to "go fast grandpa" seems to equate to 7-8 gallons of fuel. Most of the time it's just my wife and I in the boat, and we find the dual console configuration very comfortable for cruising. When we want to fish, I use the front pedestal seat and bow mounted trolling motor. She spins her seat around and trolls, or stands and cast from the rear. Works great!. When we've had our daughter and two local grandsons along it's been quite confortable for all. While we haven't tried it yet, (water's still too cold in Colorado) I'm sure we'll have enough power to pull my wife on a tube, or me (at about 190lbs) on ski's. Please note that for purely selfish reason's I didn't mention my wife's weight! Which ever boat/engine combination you decide on, I would strongly recommend a hydrofoil. I installed the one from
http://www.bobsmachine.com ( I believe it's listed as a "stablizer") and am more than pleased with it's performance. I obviously have no experience with offshore boating, but during our most recent trip on a 35 mile long reservoir we encountered 3-4 foot waves and 30mp winds that were handled with ease on my part, and only mild tepridation by my wonderful wife.
Ron