I bet that Grumman is pretty high volume for a 15 footer, though?  I used to paddle a 17 foot Grumman, and it could haul a TON of people and gear.  We paddled the Allagash with 3 of us in the boat with no problem.

I may be biased to big boats.  I am 6'4" and 250, my wife is 5'10" and 175. And I like to pole.  Small boats, even unloaded, simply draw too much water with my weight to pole well, but that's my concern, not yours.  

There may be some 15 foot canoes that will serve, but I doubt anything smaller than that will work.  Here's one that's 15.5 feet     (You need to Login or Register

Note the recommended load and displacement info, though.  My wife and I together, with no gear, already have that canoe drawing 4 inches.  Not a lot of room for extra gear, or the kids or dog, if that's a consideration.  A shorter canoe will be maneuverable, and easier to solo.  

I still think you'll be more comfortable with a 16 footer, or longer.

If you are looking for a Royalex canoe, I'd suggest a Mad River Explorer for all-around use.  If you will paddle more whitewater than lakes, the Old Town Appalachian is nice.  More lakes than whitewater, the Old Town Penobscot 16.  I don't know why, but I find the Penobscot 16 paddles much better than the 17 foot version.

All of these are symmetrical boats, so they will paddle well solo if you sit in the bow seat, although you will probably need to put some weight in the "bow" then to get the trim right.