Much will depend on where you plan to travel - ocean, river, lake. Semi-displacement can go faster with the right engines for a big
fuel bill.
Displacement is probably going to draw more than 5.5', speed is relative to actual
hull speed, Going fast takes really big engines and a lot of
diesel.
Hull speed is 1.34 x sq. root of the waterline length in feet. 60'
boat about 10 knots. A narrow
hull might raise that a little as will twin engines. I
liveaboard an 83' boat and
cruise easily at 10 knots (8.5gl/hr), and can do 12 without hurting the engines. For my boat to do 20 knots would require 2x horsepower and 30gl fuel/hour, maybe more.
Boats in the ocean roll and
pitch. Without the pressure of
wind on a sail, even more rolling. A
power boat is going to roll more than a cat. Stabilizing fins help but don't stop the roll. Stabilizing planes do a better job, but are expensive to buy and to install. There are internal gyro stabilizers, but also not
cheap and require strong
hull structure. If you're somewhere the ocean is mostly flat - S.Cal,
Texas,
Florida, it won't be too bad without stabilization.
No model recommendation. What I would pick isn't made.