For high-resolution multichannel music, you are better off staying with the same speaker brand, and preferably within the same model series, for optimal "voice matching." This often means having the same drivers in all speakers. The surrounds do not need to have as much bass extension as the front mains, but they should have the same tweeters, midrange (or woofer if they are a 2-way design), and crossovers.
I do not currently listen to SACD/DVD-A music, but there seems to be a consensus favoring monopole surrounds for that application. The notion here is that monopoles will more precisely recreate the spatial imaging as the recording engineer intended you to hear it. But beware: if any one of your monopole surrounds is less than about 6 feet from the listening position, it may "stand out" as a sound source and fail to blend in with the other speakers.
Once again, let your ears and your listening room layout be your guides.
