I think even cheap surround sound speakers are always better than TV's built-in speakers. If you don't have room for 5.1 speakers, you could get 3 front ones. (left, center, right)

Some of the 3-speaker sets can give the illusion of complete surround sound (depending on their placement and the dimensions of your room)

I can't suggest specific models because I haven't been paying attention to whats currently out there.

I bought some 5.1 speakers for about 200 bucks and there was a giant improvement in sound quality.

I agree with Jake, there are lots of speaker sets that consist of two small satellite speakers (Left & Right fronts) and a moderately sized sub that will DRASTICALLY improve your sound quality without taking up a lot of space or breaking the bank. Lots of styles/shapes/colors to choose from too. Check out some online sites like Crutchfield, Best Buy etc. to get some ideas, then go look at them in person and listen to them to help you decide whats right for you.