I agree with Internetmin that a system should be built around either electrostats or dynamics and not mixed. They really are two entirely different sounding speakers. But it appears you have already mixed them by using the Krell, a dynamic, as your center. If you are happy with these three, then use the VA's as your surrounds as was your original intention. Surrounds are the least critical to match with the LCR in a multi-channel config.
However, as VA owner myself, I would endorse the Waltz's and encourage you to try the VA's all the way around to see how you like them. I persoanlly love Vienna's and find them extremely lush and musical. They are also very easy on the eyes with their furniture grade finishes. But thats me. If you go this route, this eliminates the electrostat/dynamic problem and you would have 5 perfectly voice matched quality speakers in your 5.1 config. But with their angled enclosures, the Waltz's are really designed for on the wall mounting. Your current speakers are floor models and bookshelf, right? Are you prepared to mount the front three Waltzs on the wall? If not, then back to your original plan and just keep two as surrounds and sell the other three.
Good luck in whatever you do.
However, as VA owner myself, I would endorse the Waltz's and encourage you to try the VA's all the way around to see how you like them. I persoanlly love Vienna's and find them extremely lush and musical. They are also very easy on the eyes with their furniture grade finishes. But thats me. If you go this route, this eliminates the electrostat/dynamic problem and you would have 5 perfectly voice matched quality speakers in your 5.1 config. But with their angled enclosures, the Waltz's are really designed for on the wall mounting. Your current speakers are floor models and bookshelf, right? Are you prepared to mount the front three Waltzs on the wall? If not, then back to your original plan and just keep two as surrounds and sell the other three.
Good luck in whatever you do.