Quick question for ya'll.

I just bought a 1984 Alumacraft 17.5' flat-bottom bass boat. Tore out the console, cables and removed the Johnson VRO 70 from the back (Which I promptly sold for a little over 1/2 of what I paid to start with!). I am re-decking her (I already re-plumbed and got both livewells working properly) and converting to an electric-only set-up since there are many electric-only lakes in my area. I already have a Minn Kota Edge 70 (24V) to go on the bow. I am going to put (at least one) a tiller-style trolling motor on the transom. I am currently leaning towards a Minn Kota TRAXXIS 80. Do ya'll think that will be enough motor to drive this boat at a decent trolling rate, or should I spring the extra $150 and get a Minn Kota RipTide 101-Lb thrust saltwater motor?
I'm not wanting to pull skiers or anything like that, but I also don't want it to go 2 mph when I'm trying to get up the lake to my best fishing spots! If I can get 6-8 mph out of her that would be wonderful (I would like faster of course, but the law of diminishing returns kicks in at some point!). I plan to use the transom motor purely "to get there" or for trolling, then use the 70-Lb front motor to manuever around while fishing.

I'm just trying to determine if the 80Lb motor will be sufficient. Any and all input is GREATLY appreciated!!