http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10423&cs_id=1042302&p_id=2946&seq=1&format=2

plug this into the back of your computer (use a long-ish toslink so it would be in the front for easy access) & use the tv' toslink out as a tuner to decode the DTS/DD for the speakers. You should then NOT have to turn on the computer (you will be bypassing it), just the power on for the speakers & use the tv remote to turn up/down the sound. You then just have to remember to Manual Switch it when you want to use the speakers with the computer.

Note you may have to change a setting on the tv so it sends sound out the toslink port.

cheaper then a new sound card...