Effective ways to upgrade a Music Hall MMF 2.2


I am researching ways to upgrade a Music Hall MMF 2.2 and would like to get some advice.

1. Change the platter to an acrylic one.
2. Add a Soundbox - this is intended to be for automating changing the speed from 33 to 45 with a click - why are folks indicating this would improve sound quality? Confused about that aspect.
3. Changing the cartridge - how high can I go for this type of turntable and arm? Will get a different counter weight if required.
4. Should I consider changing the arm? When do these things become ineffective? I.e., what role does the table itself play in the quality of the sound?
5. I would like to upgrade my phono stage from the NAD PP2 that I have. Would a Project Tube Box make a difference?

Thoughts welcome.
shugho
Second Schubert, MP 150 is great for Classical/Jazz, same as Pearl for a lot less, a LOT LESS.
To recap - I should get the mat and the cartridge but not the platter and definitely not the tonearm. Please correct me if wrong.

One more question - folks online have spoken of a Speedbox adding to the quality of sound for a MMF 2,2. Apparently, this sits between the power cord and the turntable and does something magical to the sound. Does this make sense.