As to top or ceiling speakers with good bass response: (forgive the late response)
So my base 5.1 speakers are a "matched" set I bought some years ago, after reading a review on a site popular with many in the AVR forum crowd, including myself at the time.
As we know, normally when you don't include a sub, a speaker setup program, including Dirac, will set your fronts at full range. But Dirac also sets my rear surrounds at 50 Hz. In a 5.1 setup with sub, it will set all (my) corner speakers at 40 Hz. These are not very large speakers, about 13 Lbs each. But they have amazing low end response.
Formerly, in a larger room the rears were mounted high by necessity, on heavy duty swivel mounts that allow also for vertical adjustment. The mounts I believe are rated for up to 26 Lb speakers. (I once stated 30 Lbs which is not correct) I still use them today in my audio/pc room, although for lighter speakers.
So I'm saying, should I have more of these speakers, which I don't, I could easily mount them and use them for top speakers.
In fact two of my top speakers are mounted on these swivel mounts, albeit up on the wall, while the other two are mounted directly on the ceiling.
One does not need a huge speaker to have decent bass response. Whether your listening habits dictate a need for a much larger speaker is your call.,