I found the thread at
http://www.mytractorforum.com/showthread.php?t=191381
What I read was one person's opinion against a Gravely tiller.
I have a Gravely rear tiller and it will chew up and spit out a Craftsman, engine and all.
Sure you will need a liftable rear hitch, cultivator, block, gearbox and driveshafts but I believe it is worth it.
Having said all that, is it what I use once the plants are in the ground? No. I use the narrower two wheel tractor and tiller. If I had more room to put in a bigger garden I would use the 4 wheel tractor all the time. The 4 wheel tractor is significantly wider than the two wheel tractor so I can space the rows closer if I use the two wheel tractor/tiller. In the spring and fall I till with the 4 wheel tractor. It is a lot easier than the 2 wheel tractor.
Your biggest problem is the lack of a hydraulic lift. That kills the whole idea of a front or rear mounted tiller or rotary plow. That is why I suggested that you get a nice 5000 or Pro tractor with a tiller.
Once you have a two wheel tiller, the extra bits needed for a rotary plow are minimal since the drive (gearbox) for the plow and tiller are the same.
Money wise, the two wheel tractor and tiller cost is about the same as a rear tiller setup for a 4 wheel tractor. Maybe less.