Having done 3 1700+lb steers in the last three years, from killing them to freezer, I will add my comments.
Foot pedal for grinder? Yes. Well worth it. You can go buy one of the foot pedals from HF for cheap, and it makes it well worth it.
We use a Cabelas 1.75HP grinder (looks different than the ones they sell now) but it does well. We double grind the beef, and it doesn't care either time. Typically, when grinding during processing a steer, we double grind batches of 75-100lbs and it doesn't ever seem to get overly warm or struggle.
For doing a LOT of sausage, I would say get a stuffer. The grinder attachments work (we've done this with the deer that my hunting group has brought home), but a real stuffer is faster and more consistent.