CodePig made no mention of DishPro so I assume his "Dish 500 Quad" is legacy.
To stay legacy and add a 5th tuner you would have to add 2 SW44 switches in parallel using splitters (
diagram). Something similar can be done with 2 SW64s but it's even more complicated with the feed loads that have to be added.
Converting to DishPro would allow for a much simpler hookup, which way you go depends partly on the receivers you now have.
- If all receivers are DishPro, replace the Quad with a DP Quad and add a DP34. That gives you 6 tuner outputs but you will have to run 2 lines to any dual tuner receiver.
- If any receivers are legacy, or running an extra line to the dual tuner receiver is impractical, replace the Quad with a DP Twin and get the DPP44. Legacy receivers can be connected directly to a Plus switch w/o the $69 DP Adapter and dual-tuner models only need one line and the DPP Separator. Don't pay extra for the DPP Twin since you won't be able to use its input when going through an external switch.