Gordon,
Just be a bit wary when you come to fit them.
I had mine fitted by the place I got my mill from, and they have to be shimmed into the correct position to eliminate backlash and to be in the correct position for when the handles are refitted, not just bolted on. They gave me all the books and what was left over when they sent out the mill, and there were plenty of shims left over.
Another thing to be consider is that in the UK, we have to have to buy a 120 volt transformer to run them off, maybe you will be OK because you have that as your mains supply.
I think the X & Y are the same units, but the Z is slightly different because they usually cost a little more, maybe they are a bit more powerful because of having to lift the heavy knee.
All I can say, next to a DRO, power feeds are a definite gottahave. You will never regret even fitting just one, on the X axis, life is so much easier and surface finishes improve no end, so you can imagine my delight in having all three. Not because of wanting them, but because I need them to be able to use the mill.
Just enjoy
John