[H] audio decoder

[Winterlight]

I am not much of a audiophile, and have little knowledge about such 
things but I do have a set of Kilpsch Promedia 5.1 speakers. I would 
like to get a decoder that would make it easy to use switch between 
my Plasma TV and whatever. I know Kilpsch made one back in 2002, and 
they do come up for sale occasionally, but that is 8 year old 
technology, and I would think it would be better to get something 
more up to date, and less used ... anybody have any recommendations 
or advice? Thanks!