Everything on your list is important if you want it and have the coin for it.

Can you function without them sure.

If you want to target billfish the sonar is the best way to get numbers if you study and take class on how to maximize it. You can run it and make it work without a class but you can get really good with a shorter learning curve.

A chair is super efficient way to catch a lot of meatfish and or marlin. Won't use the chair for dink baits. A chair helps if a big dolphin eats a large plug. Typically you would have chair rods and non-chair rods. Clipping in on a bigger marlin requires technique and angler skill.

Can't wait to see what you get. I used to think I wanted a sporty until I knew what it costs annually to run one and travel. You can do it on a budget but I would count on 25% of what you pay for your boat as a conservative number if you are planning to do more than fish from the dock in Gtown.

30kts is fast for a 50ft boat in our ocean unless you are fishing slick days only.

Ice machine is really nice but not totally necessary.