I have a 55# 12v Terrova/IP combo, on a Alumacraft 165 cs, but you will definitely need the 80# since you have a heavy Ranger glass boat. The cruise and AP functions are great when trolling for crappie or whatever as these functions really help you in boat control and frees you up to do whatever else you need or want to do while fishing. (You can almost get bored on slow days LOL).
I'm not sure the 80/24v will pull your boat at 2-3 mph for extended periods, my Terrova 55 will pull my boat at 2.3 +/- mph at top speed but the TM battery won't last long at that speed. The TM is not designed to do that. Mine will last 8 hrs when long lining at .7up to 1.2mph(single TM battery). I don't spider rig but you can use a lot of battery if the weather or current sucks when spider rigging as well trying to maintain speed or position. Pulling cranks the speed zone is 1.5 on up depending on the day. You may want to consider putting a trolling plate on the big motor for pulling cranks. I have a trolling plate in the shed I am going to install before crank season gets here.
Some people have complained about some noise from the Terrova but mine does not make any noise that I can detect except when I make course/speed changes (just the normal noise since this TM is all electric, no cables). If you long line, some noise won't matter, if you spider rig, noise could be an issue. MG's can have the same noises as they are similar in design/build.
My IP is 1st generation (3 memory locations for spot lock and recording a track) G2 have 6 for each. IMO, spot lock does not work as advertised (5' radius IIRC) but I can use it when shooting docks. The boat will drift around some, but I take advantage of that as it provides different "shot" opportunities. The TM will take you back to the spot but can be slow to respond at times. I've read the Xi5 is better at this but I don't have any 1st hand experience. If you fish brush piles, put the bow into the wind and set the memory spot for a bit closer than you would prefer so the boat will stay in position a bit longer.
Here is a recent thread on the Xi5
http://www.crappie.com/crappie/fishi...-motor-report/