Yes, the TV has optical out, but isn't that inferior over HDMI? For example, would I get dts over the optical lead?
You would only use the TV out for TV sound. Which won't be DTS or anything like that. Might possibly get Dolby Digital from HD channels if your TV has Freeview HD but that can go over optical OK.
Plain vanilla PCM stereo is identical whatever digital medium it travels over. Provided the cables you use don't mangle the data stream of course (but then you would soon notice if they did!)