I have always admired those Scorpios for their style but im not too sure about practicality, they seem a bit like sitting in a car in terms of the seating which might become a bit annoying if you want to spend much time in one, on a boat I like to be able to move around a bit more.
Also, I'm sure you are already aware but will say it anyway, depending on the weight of the boat n trailer and tow car you may need to do the additional trailer test if you go for hardstanding type storage.
With regard to the engine power requirements, where theres a choice I'd usually go for a bit than you need on the better to have n not need principle. Also a speed boat always looks a bit daft with a tiddly motor on it imho