Welcome to TBN. A quick look at TractorData.com shows 14 PTO Hp for the B6100 and 400 lb lift capacity for the 3 point hitch, so look for rear attachments that are within those limits.
If you are looking for a tiller I can recommend the Phoenix 40 inch model. It only weighs 308 lbs and is very solidly built. We bought one from EverythingAttachments for our B5100, which is smaller than your tractor and it's almost too big for it. It tills very nicely , but our tractor is barely able to lift it. But it would probably be a good match for your larger machine.