Need expert advice: Onkyo Tx-sr803 (Zone 2 & 5.1 setup??)

I am looking to be able to use my zone 2 (FM or CD) and have 5.1 surround (THX, etc..) running at the same time.

I have the Onkyo TX-DS803

Is this possible. From what I am reading in the manual it isn't however is isn't 100% clear.

My questions (please understand the difference between SURROUND BACK L&R and SURROUND L&R before reading).

1.) it seems that the only way I can run 5.1 surround is when I plug my rear speakers into SURROUND BACK L&R. With zone two activated (ACT) my rear speakers don't work.

When I switch the SURROUND BACK L&R to SURROUND L&R and have zone two playing CD or FM I can get surround sound (playing movie) working at the same time. However, is this surround sound true 5.1 THX???? I don't think so... That is the money question!

3.) In order to get true 5.1 THX I need to have my rears pluged into SURROUND BACK L&R?

4.) 5.1 THX will not work when I plug my rear speakers into SURROUND L&R?

2.) My conclusion is that I can not play a movie in 5.1 THX and have stereo playing in ZONE 2. Is this correct?

I am looking for the facts... PLEASE HELP!

THANKS GUYS!

Anyone???

Are you 100% positive that the surround L/R speakers will work as 5.1 THX?