Define "best"
Sometimes the difference between "very good" and "best" is either negligible or, comparatively speaking, prohibilitively expensive in the real world.
Several things to consider before simply throwing money around:
1) The sub does the grunt work in a HT system.
2) The surrounds are more effective if they are above ear level. If all you care about is HT then full range speakers are superfulous.
3) Full range surrounds might make sense if you went for a multi channel music system but the results may conflivct with # 2, above.
4) Using a tower as a center channel, you would have to mount the monitor directly above the speaker. The mains would be on the same plane as the center, which would cause the sound to appear to be coming from below the visual focus. This might work for music wherethere is no visual focus, but could be a bit bizarre for movies.