"Personally, I don't think matching the rears is so important."
elevick, you are certainly entitled to your opinion. Besides the link I provided on matching front and rear, here's another one you should read, especially the last line.
http://www.avtruths.com/speaker.html
From the experience I mentioned in a previous post, I have heard more HT than most people. No doubt the best sound is achieved with all identical speakers. As sound moves through the room or sound is being created by 2 adjacent speakers (possibly on L or R side using front and rear speakers), the blend is absolutely seamless through the entire room, and speakers disappear. Timbre matching comes close, but still not quite as good as all identical. Mixing brands degrades even more. We use matched speakers for a 2 channel system, so it just makes sense to use matched speakers in a multi channel system.