I did the same with my 7.1 Onkyo. Makes a pretty big difference as Pup said. It's a middle of the road system and the HDMI ports started going out last year but I love it. Couldn't see paying more for what we use it for. I just run my HDMI to TV and a single Optical over to the surround. Cleaner setup that way anyway for my situation.
Have noticed something strange this week with my new TV. The HDMI cables I have are apparently attrocious. Signal won't even cause tv to recognize a picture at all on some things and on others the picture and sound flickers constantly. I just notice it when watching 1080p content. After finding a good cable, I tested all devices and they all work with it on any port, but depending on other port and cable combos, I get nothing or constant flickering. Ordered a complete new set of 3 HDMI cables to see if it helps. If not, looks like the TV may be going to Panasonic for repair.