Much under rated and often an after thought, the loudspeakers are the CRITICAL part of your entire HiFi system and make a huge difference. Stereo systems need two speakers - Left and Right - as large as space (or the partner) allows. Surround systems and home theatre need more, possibly five and perhaps six speakers altogether though the size of each may vary. You still need two main Left and Right speakers - the majority of sound comes from here so these need to be as large as practical. The remaining speakers are: - center dialogue, rear left and right and sub-bass. The sub-bass speaker can go anywhere in the listening space as its location is not important. So what about the remaining three effects speakers. As the trend towards full surround sound grows, the importance of these speakers will also grow such that the quality of effect is determined by these speakers. If your budget and space allow, go for a matched system with the same type, size and especially make of speaker. You can economise by downsizing the effects speakers to a smaller version with some loss of effect. However, all the information about the need for top quality Point Source speakers applies equally well to the effects speakers.