The money you put in to go faster will take a one way trip. Most buyers of a boat like that will want stock type power so if you do upgrade with the intention of selling it someday stick with the merc stuff.
Realistically you have to decide how you want to use the boat. If you are going to trailer it than go ahead and hop it up as you can still trailer that one with a std pickup. If you want o get a place at the Lake then sell it as a longer boat will ride better on the weekends which is when you will spend most of your time there.
If you want me to decide for you I need more information.