Yes the air ride seat will make a big difference. OEM Kubota seats generally suck and give very little suspension. You can get a Grammar air seat which should bolt on to your machine relatively easily.
FYI I put one on my ZTR for the same reasons. I was hesitant to do it because of the cost - I have no regrets other than I should have done it sooner. I need to do the same for my M59 because the OEM seat really sucks on that machine...no suspension and it's tilted so you feel like you are constantly sliding off the seat.
I figured I would cross reference the dimensions of my existing seat to a Grammar. Since there isn't a Grammar dealer near me, I'll have to give them a call to see if they have a basic seat with the suspension only. I don't need the seat to be heated, etc.