If you think even QS4's are "too big", then I think almost any conventional box speaker is going to be too big. Just get some in-ceiling speakers and be done with it. Emotiva was having a sale I think, but I have no experience with their products. There is a school of thought that in-ceiling speakers are not of sufficiently high fidelity to warrant much fuss, and the Dayton ones at Parts Express seem to get good reviews. Good luck and have fun.
I think Mr. Tomtuttle is right once again.
Whenever I first read this and keeping in mind of my personal experience and the rave reviews of the QS8/4's my initial thought was what would be a comparable surround speaker to Axiom's QS surround speakers?
