connecting hdmi cables?

my onkyo receiver has 5 hdmi in ports and one out. T.V has 3 in, and cablebox has one out.I have one hdmi cable out from cablebox to tv. no problem. the question would be how do I get sound through my receiver if I want more sound than just the tv speakers when watching cable tv? I dont wish to just run the cable box hdmi out to the receiver because most of the time when im home to watch regular tv I have roommates sleeping and my audio system is too powerful, and at 4000 watts plus, will be too much draw on the electric bill for everyday use. would one solution be to just use the red,blue,green cables from cable to tv for just everyday use, and then use the hdmi out from cable to receiver for the occasional stereo sound be ok? if i do that am I just lowering the picture quality from true hd because of the co-ax cable connection, or does the hdmi source become the "master" in effect and override the RBG connection. I am just a little over my head here. if there were two hdmi outs on the cablebox it would be too easy but there is not. RATS!