Woody,

I've never cut my peace lily down to the soil line, so I can't say if it's good, or not good to do. Personally, I wouldn't do it unless the leaves happened to get torn and tattered from lets say, a giant wind storm, or a blender mishap.

You might want to consider cutting and re-potting in the spring, before the flush of new growth.

You can simply cut the plants root-ball into as many sections as you like using a sharp knife. If you want to pot up just two potted plants, which by the way can include more then one plant per pot. Just cut the root-ball in half. If you want more, cut the halves in half, so on and so forth.
You can also pot up just one plant per pot getting rid of the rest, whatever way you want.

Start by taking the whole plant out of the pot, root-ball and all and cut from the top of the soil down to the bottom. just like you were cutting a piece of birthday cake, or bread.
Get as many roots as possible per plant, or bunch, shaking off some, or most of the soil, then plant the sections into their own smaller pots to either keep, or give away.

Billy Rae