For a second non HD receiver just hook up yur R6 cable directly to your 91 satelllite transponder. Almost all non HD channels are on 91. You may miss a couple of channels such as Cool Tv. If this bothers you buy another SW21 switch and hook it up like your HD receiver.
If you go to three receivers, most people use a SW44 switch that replaces the SW21s. This will give you outlets for 4 tuners and would work with say a 4100, a 6100, and a dual tuner 9200. The SW44 comes with the 9200.
Take Fuzzy's advice for any more details as it's a real good site.
Location: Close enough to make a beer run during a TV timeout
Exp:
And the moderators are really cool too.
But yes, hooking the non HD receiver into the 91 LNB is all you need to do. After 2 receivers you need an SW44, and that allows you to hook up as many as 4 receivers. See diagram#3 here: http://www.digitalhomecanada.com/for...ad.php?t=26721