We need a little more detail here.
First you have to decide on what size implements you want to run. That will dictate the size of tractor.
And you also need to think about what other tasks you want to do with the tractor. Any tight areas you need to squeese between that would limit size? Garage door height/space? etc.
And what dealers do you have in your area? Do you perfer a certain brand?
And then I would suggest you take a trip to your nearest dealer of any brand and LOOK at them in person. Jot down some of the model #'s of the sizes you think you want and report back. You cant go on just HP. You heed to look at the frame size of the machine (physical size). Because just using kubota for example, a
B3200,
L3200, and GL3240 are ALL 32 HP machines. But there is a HUGE size difference when you actually see them.
This is also true for other MFG's. In the 20-30 HP range you mention, there are two basic sizes. Sub-compact-utility-tractors (scut) and compact-utility-tractor (cut). Typically the CUT have a FULL category 1 hitch. The Scuts being smaller have a limited Cat-1 or even a cat-0 hitch. It does make a big difference. And without trying to start a debate and hijack this thread, there are some people who feel a SCUT is not much more than a glorified lawn mower due to their much smaller size.
So if you can get to a dealer, and decide between a CUT and SCUT, we will be much better able to help you out.