A small tiller should work. Usually the 4-foot wide single tined shaft at most place. The King Cutter is a good brand (aka Gearmore). These can be found at TSC, NorthernTool and Rual King without too much trouble. Just shop around for the better pricing.
Yes, read the other thread of the FX32D and a tiller too. The 48-inch wide (4-ft) tiller would be within your Yanmar Hp needs.
I'm in the search as well for the upcoming growing season. I have a Poulan Pro garden tiller that was $700 new. Now with the Yanmar I hope to sell that item for a tractor tiller.
Also, some of these smaller garden tillers for Club Cadet, Sears and JohnDeere CAT-0 machines would work with your Yanmar too. It just depends on how much land you plan on tilling and how deep.