SW-21 will not work with Dishpro lnb's. The dishpro equivanent is the DP-21.
If you get a Dishpro Twin, it has a DP-22 built in, so it will feed both 82 & 91 to 2 recievers. A dishpro Quad will do up to 4 recievers.
For what it's worth, a Legacy Twin or Quad will do the same. But if all your recievers are dishpro compatable, go with the Dishpro.