One of the two major DIY sales companies is offering a good price on the Vifa TC9FD25-08 3.5 inch mid range. FR is +/- 2 db from about 80hz to 8500hz. No distortion measurements made.
Combined with either my dome treatment or a good ribbon AND stereo woofers, you could make a pretty dynamite array.
Remember that you will need to to have the woofer array be at least 5 feet high to get coupling with the floor to ceiling, and that the nearfield for for each line is roughly 3 times the length of the line.