Q300's all the way around, even using one as a center, would be an excellent (some would say ideal) setup for HT purposes
The "ideal" home theater setup is using identical speakers in all positions (except the sub of course), or, at the very least using three identical speakers up front LCR and identical speakers for all the surrounds/rears.
Some common and understandable compromises to setting up an "ideal" surround system are:
- limited space for a center speaker forcing the use of a different center speaker than the RL mains, usually a horizontal center speaker.
- wanting a system that plays both music and HT well, usually leading to "stronger" LR mains, often towers, that are different from the rest of the speakers.
- budget and/or space constraints affecting the surrounds/rears speaker choice.
If space is an issue for the center speaker you can lay a Q300 on it's side (it's only 8.3" tall then). The KEF Q100, Q300, R100 and LS-50 are somewhat unique in this regard since they all use a single concentric driver. It is not advisable to lay most other speakers on their side.