I'm in your position, Gary. C-Dory on order, electronics choices being made. I've got two commercial fishermen as stepsons, one in Alaska, this moment heading for Kodiak and crab season, the other fished out of Barnagat Light NJ 'till he got smart and quit. They constantly preach "Furuno separates." They have the luxury of room and a penchant for the high end commercial stuff. On the other hand, keeping the "simple C-Dory" simple says a lot for combined units. It depends more on your budget and the actual (not perceived) end use. Where are you located? I think it makes a difference.
Right now, just like listening to the constant nitpicking among Ford Chevy and Dodge diesel pickup owners, you're gonna get lots of opinions as to what's "best." RayMarine, Furuno, Garmin, and Lowrance all put out dynamite chart plotter/GPS combos with sounders. Furuno and RayMarine have nice radars as well as great sounder/fishfinders (now that RayMarine solved their software problems) and as your dealer pointed out, they both have beautiful display choices and fully integrated systems. Their target market is the 34-38 ft. sportfisher market and they do well there. Are they "overkill" on a C-Dory? Not at all. Are they absolutely necessary? Nope. You're absolutely right, Gary. It's bewildering. A Furuno GP1850WDF with a JRC 1500 MkII radar was my "final answer" for almost a month. Two units, but the radar display is easily removable and stowable on board, so it's only taking up a little room, is still there for an emergency, but keeps my wallet happier. Here in the San Diego area, a radar is rarely used. and the budget fit my limits, plus it would keep the kids off my back. Unfortunately, the 10" displays are mighty tempting, especially with chronologically disadvantaged eyes like mine.
Don't discount the possibility of a used system either! Die hard fishermen are constantly upgrading and switching to the "latest and greatest" if it will give them even a tiny advantage while hunting Yellow Fin Tuna, Albacore, or Marlin.
http://thehulltruth.net/ or
http://www.allcoastsportfishing.com trade/barter and electronics forums will give you even more bewildering choices with occasional great opportunities. Certainly more information than you can imagine!
Bottom line? Have fun and let your checkbook make the final cut. Mine finally did. I picked up a slightly used Lowrance LCX-104C combo with the 10" color display for half the new price. Not a scratch on it, the latest software will read Navionics Gold charts, I can play back my entire trip at home on my desktop PC afterward, and my eyes are happy too. The seller? A 38 ft. sport fishing boat owner who decided to upgrade to the Furuno 1833C NavNet system.... Did I save anything? Naw. It just gave me room to buy a stainless steel radar arch/rocket launcher combo as soon as now....
Happiness is spending yer kids inheritance.