The Denon AVD2000 is better than the other decoders in the $200 price range. The Denon can be had for as low as $125. You have to check fleabay, and other sites like AudioReview (for sale items forum), etc..
You will have (6) channel "outs" from the decoder(s) or optical output that carries all channels. Some of the PC dd decoders have a built in amplifier for each channel right in the decoder itself, and you would just connect your (6) speakers directly to the decoder. On decoders like the DENON.... these outs can go into (6) seperate amplifiers (each amp you could run 1-4 speakers from), or into a (5) channel amplifier/receiver, etc.. You can have as many as (6) seperate amplifiers with more speakers than you would ever want. This is how I have my home theater. (4) speakers per channel for a total of 24 speakers.
Then there is "bi-amping" and speaker "bi-wiring", it goes on and on.
It really depends on what you want the decoder for, and what you want to spend.
But, I was mentioning that one consider a decoder that has more flexibility. I think for a small room... the PC decoders like the Desktop Theater 5.1 decoder... are adequate.