Dear TS,

I disagree, there is no reason why a surround channel should use Floor speakers.

Surround channels is used only to supplement the front speakers for the "ching" ( or other soft) sound that you cannot hear from the front because you are seated to far.

Further more I would not call it a "sound system" if you are using Floor speakers as surround channel, a proper name should be "Noise System"

Not that you cannot use.. you can... your AMP also needs to be powerful enough to be able to carry the additional watts to sustain the bigger speakers. either that.. or your amp kaputs.

Well good luck.