If you don't need 5.1 surround sound then a soundbar can be used for increasing the sound effects. They have a subwoofer and a soundbar which handles the Left Right signal. Soundbars with optical inputs are not cheaper though.
Boston Acoustics TVee Model 20 Soundbar
Junglee.com: F&D T780W TV Soundbar
Yes, what you say is very true. However, the reason why I suggested a sound bar is because if you use a DAC (digital to analogue converter), you will only have a Left/Right RCA output -- which is exactly what a sound bar has. On the other hand, a 5.1 speaker set up will have 6 different inputs, so using a DAC will not work.
However, yes, sound bars can get very expensive themselves, as there are varying qualities of sound bars. I would highly suggest that you go to a showroom to see what sound bars are capable of before buying one if you are interested. Personally, I think sound bars are great and saves the hassle of all the wires from a 5.1 speaker setup. Even if you buy a wireless 5.1 setup, it will be very, very expensive. In addition, a lot of sound bars can "mimic" surround sound by bouncing sounds off of walls and such. How effective the virtual surround sound is is entirely subjective, however.
LG WRman Sherlock, out!