kayang kaya ng PC speakers yung 20 sq. m. it's not that big a floor area, parang room size din yun. the sound quality is a different discussion altogether, but as far as volume is concerned, you'll find it acceptable. my cambridge soundworks FPS2000 4.1 set fills a room enough for my ears (though i use my sennheiser more often hehe)
logitech Z line is a good series i think. for HT, you'd want strong, tight bass, and the logitechs are one of the better ones in this price range. the creative subs may underwhelm you for this application, and they get boomy all over the place at higher volumes. keep in mind that subs work best when placed in a corner of the room or at least next to a wall (depends per sub), and you'd want sturdy speaker stands for the satellites





Mas malakas na daw bumayo.... yun ang nabasa ko. 