I curently have the same setup as you, 950/7100 combo setup in 5.1 instead of 7.1 mode. Everything works with mine.

Try using the left surround and right surround channels instead of right surround back and left surround back channels.

Using multi-zone in page 29 of the 950 manual should help you setup your system. You must use the analog output of the source (cd, dvd) player at least that's what the manual states. I haven't tried it myself though.

Hope my suggestions helps. Anyway, how do you like your SVS sub? What model do you have?