I'd say get an integrated 5.1 unit or perhaps a blu ray player that comes with it's own 5.1 system. I got a decoder + speakers, but cabling etc adds a lot to the price and it's not cheap to start. It's a great system, but costly.
Also, have you made sure you're playing the movies in 2.1 sound? IF they're set to 5.1, you'll be losing a lad of the audio on a standard setup.