I'd suggest scanning this forum for answers to just about all of your questions.
I did some fairly extensive searches here but I was not using the right terms. Maybe I should have posted in the newbie or beginers section.
Eventually I did find a kink to an article o another site that the "original" Surround Sound is now referred to as either just "Dolby Surround Sound" or "AC-3".
All newer Dolby Prologic modes are by design backwards compatible to the level of your decoder. So anything from 5.1 to 100.1
should play back on my sytem at the AC-3 Dolby Suround Sound mode from the two signal stereo signal.
What I have not been able to find out directly and I suppose I just need to experiment is the three options of incorporating my sub.
1. Run full stereo signal to sub from receiver (current set up) using the subs built in crossover to the mains. Crossover frequency in theory is set to 60-70 hz but my daughter likes to play with the knobs
2. Run the sub out LFE signal from the Pioneer only to the sub. This would result in one speaker pathway for the Pioneer CD, DVD, SACD using the sub but nothign else would have access to the sub.
3. My sub has a secondary right and left input RCA stereo input to where I could run option 1 and 2 at the same time but I don't know if this would be good or very bad for my gear.
Any advatages or problems with trying both sub inputs?
Thanks