Another option people seem to forget about is the Woods 54" RC. It's offered as an alternative for people with smaller tractors. I use it with my Ford 1510 and love it. Your tractor makes more power than mine, but it's also much lighter, and as others have pointed out (tail wagging the dog), that can be some cause for concern.
A common problem nowadays, IMHO, is the tendency for manufacturers to put more power in smaller packages, which can make for a compact powerhouse, but makes actually using and handling implements near the outer limits of the machine's capability an increasingly dangerous practice. For instance, your Kubota makes 30hp (22PTO)and can power and lift more at the 3-pt hitch (1655 lbs vs. 1432 lbs) than my Ford @22hp (19.2PTO), but can it handle it? (Tractor weight= 1740 lbs vs. 3200lbs) Rotary cutters leave a lot of mass hanging several feet out the back of your rig. Tractor weight is your friend.
Sorry if I muddied the waters. :ashamed:
Joe