For the bow mount, I would definitely get the universal sonar...if you have to attach the 'ducer to the motor it leaves the unit itself and the cord exposed and they WILL get damaged. Also, since you will probably be using the bow mount for actual trolling, get one of the non-cable drive units - the cord on them is long enough to control the motor from anywhere in the new boat.
Oh yeah, I would go with Minn-Kota...the 24V 74lb thrust model has more then enough power for my 17' Lund. It will make headway into a steady 30mph wind on only the "40" setting. (it goes up to "100")
As for transom mounts, I think Minn-Kota has a really funky looking unit that has some really neat features.
don't forget about chargers.
I would get a 3 bank onboard charger, 2 banks for the trolling motor batteries, the last bank for the cranking battery.