Rack04,
I would suggest you go to the websites of Pioneer, Onkyo, and Yamaha and read the manuals for the receviers you are considering. As you are just learning about HT and all the connection options, a decent manual and easy to operate receiver is going to be important.
You have flip flopped between Onkyo 502, 602, 601 and Yamaha and now Pioneer. IMO, the Onkyo is the easiest to operate and their manuals are actually understandable. Yamaha has the absolute worst manuals and are needlessly complex to operate. Can't say anything about Pioneer as no direct experience there.