OK. The answer is simple Dish 500 with Legacy Quad. Period.
The Quad has 4 outputs, each one will, at receiver command, transmit any of the 4 transponder bands needed. Legacy because you have Legacy (4-digit model number) receivers, and the newer receivers can use lder LNBFs.
Don't screw with external switches when you don't have to.
There is NO point at all for you to be considering getting a Twin, using a pair of Duals, or any other setup other than a simple, basic, straightforward, no hassles whatsoever, Legacy Quad.