With a budget like that, I'd strongly recommend you not buy computer speakers. The 2.1 systems typically sold for computer use are less than ideal - the satellites are generally of only moderate quality, and the subwoofer is therefore being asked to pick up some fairly high frequencies which should be handled by the main speakers. At $300, you start to get away from this effect, but you're not necessarily getting good value for money.
When you've got a budget like that, you might want to look at good-quality bookshelf speakers and ignore the subwoofer altogether. There are a few compelling choices with integrated amplifiers, such as the
AudioEngine A2 set reviewed by SPCR. However, you could also buy a small standalone amplifier (I have one of
these, and have been very pleased with it), and use pretty much any bookshelf speaker on the market.
If you go with bookshelf speakers, you might not get quite the bass kick you would from a 2.1 system, but you're likely to end up with much higher sound quality and much smoother frequency response. You should also find very respectable bass - good bookshelf speakers often have -3db response down into fairly low two-digit frequencies. The sub bundled with a 2.1 set would play a few key frequencies much more strongly, but actually not play over nearly as wide a range.
or movies in PC) , listening to music, etc. I do not look one that only provides a good volume, because as said previously i live in apartment, but a optimal distribution of sounds and the quality of them(with a good bass for movies 
), without noise. 
