If you really need to open all those ports inbound then I can't think of a way to do it because you only have one IP address on the WAN side of your firewall (and each IP address only has one of each port number).
You're sure it doesn't just work by making outbound connections? (in which case you don't need virtual servers at all, and all 3 would probably work). The directv forums seem to imply you just connect and off you go, which would imply you didn't need the virtual server ports set up (but setting one up would almost likely break the access for the other two units).
I'm not sure how the special apps rules work on that model firewall but it might be possible if you can configure a trigger port to allow connections to be opened for a short time based on outbound access to a particular port. Some of the 3Com firewalls work like that, others just have a list of apps/protocols to allow and no ability to customise (though I guess directv might be in that list these days?)
Apologies for the slightly vague answers, as you can tell I don't have your model of firewall or directv, just more general network/firewall experience.