Tooner2, I think I'd suggest taking a demo ride before you buy anywhere and I'd take some friends with you if possible to simulate an actual load. That way you'll have a better understanding of what 50 HP will do. But, as other's have said, it sounds like you'll be boating some fairly big water, so extra HP might come in handy, particularly if you need to get somewhere quickly.
Obviously, most of us are working with a budget so a pre-owned Benny may make perfect sense.
If you do end up trailering it from MN, definitely go with a radial tire. I live in a pretty good sized city, but when it came time to replace a bias ply trailer tire, no body stocked them! It would have been a real bummer if I was stranded on the side of the road.
FWIW, here's at least a partial update:
1. A $7k difference in the price of boat/trailer combo ($6k on the boat alone) pretty much determines where I buy the boat--and yes, both dealers were working from the exact same build sheet and both had to order the boat, given the features I wanted (one of those being the privacy curtain--I've reached the age where a 3 hour cruise necessitates a couple of potty breaks, and in mixed company I can't just haul out the PVC pee shooter and let 'er go over the side in plain view).
2. You guys have made me think really hard about my choice of motor size, but I'm likely to stick with the 50 h.p. Yammy. My reasons: a) I might get to big water like Havasu 1x or 2x a year, and then it would likely be with only 4 adults on board. If we have to run, er, slow-walk for cover because of the weather, well....I guess I'll have to pay close attention to the weather reports; B) the other 98% of the boat's time on the water will be on the river below Parker Dam. I've been on the river aboard an 18' with a 40 horse motor and 6 adults, and a 21' with 4 adults and a 50 horse motor. Yep, they were slow movers (the 21' Leisure with 23" logs topped out by GPS at 15 mph traveling upstream with 4 adults, sans beer and snacks). But for us, the toon will be little more than a slow cruising, open-air living room where we can sit around and socialize with a few friends on the water; c) if the boat returns to MN, the 50 hp configuration is extremely common and the hp would not adversely affect the resale price--just the opposite (you might be surprised at the number of 18'-20' MN toons that are still powered by 25 hp motors, although that may speak less to the laid-back nature of MN tooners than to the size of many lakes here).
3. Sharkhide. I'm convinced. Never knew anything about it before getting on this forum. I'll do it myself right after I get the boat. Bimini and furniture will get 303 Protectorant treatment--regularly.
4.Docking lights--maybe not. I'll see what they cost. High-powered LED flood/spot lights are pretty inexpensive these days.
5. Trailer--might have to get that elsewhere. Dealer sells Yacht Clubs. From what I can tell, YC comes in two configurations in the size I need. 4,500 lb tandem axle with 12" radials, and 4,400 lb tandem with 13" bias ply--both Carlisle brand tires. A 2,000 mile trip dictates radials, the condition of the highways around Flagstaff dictate minimum 13" wheels. I'll see what the dealer will do by way of crediting the bias ply tires so I can put on a set of Maxxis 13" radials/wheels (he did agree to that when I was giving thought to going with the 12" radials). If I get the trailer elsewhere, I'm thinking MidAmerica based on my research to date. Any observations about trailer or tire quality are welcome--as are any other insights you care to offer.
I said I would update y'all, so now you probably have more info than you care to read. As for me personally, I appreciate your insights and advice, even if I decide to pursue an approach that departs from the consensus. At least my future regrets about ignoring your sage advice won't come as a surprise.
Thanks.