Polk, Deftech, and Klipsch are all reliably good brands. Their speakers will be fine, but you can do better in the subwoofer department. For subs, in that budget I would be looking at Hsu Research, SVS, Monoprice Monolith, or Outlaw Audio. Those manufacturers also make good loudspeakers too, so a 5.1 setup from any other them would be very good. Some other good speaker manufacturers to look at is Ascend Acoustics, Philharmonic, Infinity Reference, JBL, Paradigm, and there are many more.