Use the boat as is and see if you like it.

I have a 20 with a 225. Fast boat. I do understand other that like having a smaller motor so they can plane at lower speeds. However it all depends on how you use the boat and the sea conditions that you will see on a regular basis.

Backrest
 

I am unable to steer the boat while using the backrest. I wish it was removable because when you go fishing you can leave it at home but for cruising you can put it on.