Re: which upgrade first?
If your 40HP gets you there, unless you find a GREAT deal on a 90HP with controls, I don't see a great bang-for-the-buck.
I don't know nuthing about no MinnKota anything.
If your main concern is fishing, the newer Humminbirds with the side scan and down scan could be pretty cool, depending on your fishing area.
I just got a Humminbird 798cd HD SI Combo w/GPS, and once you figure it out, it is way cool.
It's great for finding structure that fish hang out at, that aren't on any charts.
The second day I used it, I saw something that looked like a bunch of fish hanging around a bicycle. I happened to have gotten stuck on a bit of a muck-bar, and while de-mucking my boat, I walked over to it and discovered.... a bicycle.
95% of the time, it really isn't that useful. When you find some weird structure, hit the 'waypoint' button, and you got yerself a nice secret fishin spot to check time after time...