Your Onkyo supports HDMI ARC? if yes....no need extra cable...the HDMI cable from AMP MONITOR OUT to TV HDMI IN will serve the purpose already... but not sure need to set something or not...
If not support HDMI ARC...just connect an optical from your TV OPTICAL AUDIO OUT to your AMP OPTICAL IN (probably choose the TV input)....
3DTV: Panasonic P42GT20H (Nano 305)
AMP: Pioneer VSX-1020 (MAS 50A HP)
BDP: Panasonic DMP-BDT300
F: Roger CS9
C: Bose VCS10
S: AR
SB: Atlantic 153c
FH: MB Quart 460
PB: Belkin Pure AV PF-30