I currently have a 942 and 921 connected using a DP34 (DISH 500 and 148). All DISHPRO equipment. 2 cables coming from the DISH 500 and one cable from the 148 dish. Therefore a total of 3 cables feed into the DP34 and then 4 cables go to the two receivers (2 each). What would be the best way to add my 721 (which I'm currently not using) into my setup to have 3 receivers (all with 2 tuners each)? I know that both the 942 and 921 are dishpro plus receivers (the 721 is only a dishpro). Thanks!