I assume you mean 4 receivers and you want to add 2 more?
What receiver models do you have? Reason I ask is if they are 4 digit models (6000, 4900, etc) you need an adapter if you go Dish Pro
If they are all 3 digit models, then you could go DishPro
You would need a DishPro Twin and 2 DP34 switches
-replace the 2 duals with the DishPro Twin
-run 2 lines from the LNB to the DP34 switch
-hook up 4 receivers
-there is a loop out on the switch to attach another DP34 switch
-add the 2 extra receivers and do switch check on all of them
If you have Legacy (4 digit model) receivers, then there is another way