I bought A Sony KDL-46XBR4 46" HD LCD TV and a Sony BDPS350 BluRay player

. I would like to know what kind of equipment I have to hook my BluRay player and HD Cable TV box to so that I will get the 5.1 sound that I should be getting. I tried hooking the Cable box and BluRay player to the TV via HDMI cables and then connecting the TV's Digital Optic Out port to my old Samsung home theater's Digital Optical In port via optical cable. The Samsung sends the sound to the speakers but is obviously not "decoding" anything. I am not going to hook up anything else so I do not need some huge device with tons of in and out plugs nor do I need 100 watts a channel output (small house and close neighbors). What I really would llike is something that decodes most systems and is reasonably (cheaper the better) priced. Thanks for any suggestions.