As far as I know, angels can be very difficult to sex... I think some people who have dealt with them for some times have come to be able to sex them, but the average joe might find it very difficult. The only easy way is by looking at the papillia, which is only out when they are getting ready to breed. Good inverts would be things like snails, amano shrimp, ghost shrimp, etc.
7.6 is a perfectly fine pH for angels. I would definately avoid using any pH altering chemicals; they tend to be very unstable and you have to use them all the time. If you have a high kH, they simply may not work at all.
7.0 is not necessary, I think so many companies stress it because they want to make a buck off the unexperienced, though I'm not positive on that. As JSchmidt already said, stable is more important than 'perfect' pH.
HTH