I like the idea of "sound waves" in #6 and
#7 though I think
#7 would be better without the black "waves", which look slightly bird-like.
#4 and #5 are better than two, but I think the hearing/listening concept is definitely better still.
I'm not sure about colour. I've never felt blue and yellow go particularly well together,
#1 is still first. I don't feel particularly strongly that the logo HAS to be blue, though the advantages of blue are (1) I'm using it already, (2) No-one else in this market is.
If you want to try additional imagery, a pulpit is a possibility, though I don't suspect this would not work as well as a bible.