I'm using Profile 908s as surrounds with Diva Utopia Be's and the CC 1008 Be. They have worked hard to "voice" their lines as close as possible so that you can mix and match. I don't notice a difference, especially since the surround channels are not used as heavily in HT as the main and center. Also, they are behind as opposed to in front of you, so it would be difficult to hear a huge difference anyways.
I don't think it would be a problem to use the Electra 906s as surrounds for the Electra Be's. Good luck.
I don't think it would be a problem to use the Electra 906s as surrounds for the Electra Be's. Good luck.