Concerning direct radiators at rear for SACD, you generally want side speakers for surround music. This is regardless of whether direct or diffuse speakers -- they work better at the side, roughly 90 degrees, but from 80 to 110 is probably OK. The rear speakers are generally for HT, not music. In theory digital receivers with DD/EX decoding can extract 7.1 from 5.1 sources (inc'l music), but it won't work for SACD or DVD-A since these are analog.