Option to decode dolby / dts

I would like to know if there is in the market an option to decode the multichannel audio from movies that is not a proccesor or receiver?, let me explain: I use a small computer to play / store my movies. If I want to decode the audio I need a proccesor, but what I love to have is a small external device - like a dac is for regular audio- that I can run a hdmi cable and from there run rcas to my power amps (hope idea is clear), Any suggestions?
Thanks in advance
There are inexpensive S/PDIF versions, although they do not have volume control. Can you use those? Finding an HDMI 5.1 converter is harder. If you are not using the lossless codecs, you can buy an old receiver that does 5.1 conversion with pre-outs for not much money, although they are not small.
Thanks for the responses; thats what I thought. My idea is to have a small sxternal surround sound processor that can convert the digital audio signal of my movies to analog (Dolby and DTS in all its options)and control the volume with the computer program that Im using to play the video. The intention is not to have a big processor in my system just a small surround processor that just that job and nothing more: no multiple inputs,etc.
I am interested in this also. For me it is wanting to convert the 5.1 into 2 channel (PCM?) so i can use my Tascam DAT player as a DAC. I would never, of course, record any Great Performances or Austin City boundries. All I get now is a chatter noise when I go from the cable box to the DAT. Alot of people say there are hidden menus on the cable box but I can't find them. And no, I do not want a surround receiver.