Some televisions have audio out capabilities that allow you to connect an external speaker to the television's internal amplifiers. The more common audio out is a line level signal that would require additional amplification. The best fidelity will be attained by by-passing as much of the audio electronics in your television as possible and using external amplification. I would recommend that you use powered monitors to add surround capabilities. It will keep your system as simple as possible. Go to a Guitar Center, or similar store, and check out their selection. The brands (KRK, Event, Mackie) aren't well know in audiophile circles, but they are high quality products. A set of $400 (sale price) powered monitors can easily do the job.
BTW, it is my experience that surround sound really dosen't add that much to the movie experience.