Hello, I am very new to this and have never researched or hd a surround sound system. I just purchased the Polk audio TSI500 speakers for $100 each (bought 2) at Fry's. now I need some rear speakers, a subwoofer, a center speaker and also a receiver. Which one of these is the most important and also based on my TSI500 front speakers what are your recommendations. I would like to keep the price point as low as possible. I would be okay with a beginner or should I say first time surround sound system. I believe I got a good deal for those speakers from what people have said. Of you could please be specific in what I should look for in the speakers, subs and receivers. Like I did earlier price is a major factor.