Grinder for making pork sausage

Hi!
We have been raising pigs for a few years now and have about 9 producing sows and sell a lot of piglets but sometimes we get pigs that don't sell and will have sows that are worn out and need to be butchered.
I need a sausage grinder. I just want ground sausage, course or fine. I am not going to make sausage links, just loose sausage that get blended with spices for patties and meatloaf. I can foresee grinding a lot of sausage at once maybe 400 pounds per year. In other words we need a semi-commercial grinder that has a motor and can take some hard use.
Does anyone have any suggestions? The internet has Many to choose from but I don't know where to start. Does anyone have suggestions?

I have used my Kitchen Aid professional for over a decade.
You can buy a meat grinder for it. We have ground alot of poultry and deer over the years.
I also have a flour mill for mine. I am on my third flour mill. We wore the other two out.

Kitchen aid pro or Bosch both can handle that and still be used every day as a mixer in the kitchen.

Like Alex and R Scott I would recommend the Kitchen Aid attachment, unless you don't want a multi-function tool for this.

For large scale grinding you want a tool that has enough Horse power to get the job done and last a long time, Hobart is a commercial kitchen machine company and while it may seem pricey, their products last for at least decades if not centuries when well maintained.

We use our Kitchen Aid Artisan mixer with the grinder attachment but we only grind one hog (approx. 50 lbs. to grind) per 6 months for our own use.

I've got one of these
http://www.trademe.co.nz/business-farming-industry/retail-hospitality/kitchen-equipment-supplies/other/auction-1072118381.htm
They're Chinese but work really well. We usually do two pigs at once, I bone out while someone else feeds and bags mince. It goes so quick that I can't cut quick enough, we tend to do 40-50kg of mince at one from multiple wild pigs or an entire deer minus the main steaks

Here's what we went with for the equipment in our small on-farm butcher shop:

http://sugarmtnfarm.com/2014/02/06/equipment-choices-for-butcher-shop/

For the grinder it is a Hobart 4822 Meat Chopper. After using it for months I'm very happy with it. I'm glad I got that size. Small enough to fit in my small cutting room but the biggest power in its line.

I would suggest stainless steel and plenty of power.

Don't grind the whole sow. There's a lot of good cuts on a big sow. I have chefs lined up waiting for the big bellies and other things. The tenderloins and chops go to stores. My favorite cut is the Boston butt steaks off a big old sow. Excellent eating.

-Walter