That depends on budget and usage. If your going to be doing small batches then Kitchen aide attachments or the cheaper electric grinders(like pro waring's found at retail outlets)may well suffice. Though if your going to be grinding a good heapat one crack or several through the yearthen your better to buy something that is 3/4HP and has stainless steel gears/bearings (ie: LEM, etc).

I do custom processing of game as a sideline and use a 1 1/2hp Torrey which makes short work of grind but it also costs some extra money and isn't really required for individual usage.

I have used everything from hand cranks up to commericial units, they all work untilyou exceed the usage model. IMO, the cheaper plastic gear grinders are fine for upto 20lbs in one session. They require some additional cutting to feed and work well in the smaller hopper/mouth. Anything larger I say buy a 3/4hp/ SS gear unit and be done with it (time saved and less money in the future as the little engine will not go forever if being over worked). If such an expense isn't in the cards a hand crank and some elbow grease may be the way to fly for the time being.