If you're working with RED/4K+, then actually that 32gb of RAM is totally fine, and more would not be too ridiculous. We've been routinely burning through 50gb+ when editing a ton of Dragon footage.
Titan Z is totally not worth it. You'll get real-time playback of 6K with a Titan Black, and it'll cost less. It's not just that the Z is overkill, it's just a bad deal. Performance doesn't match its price.
If you aren't working with RED/4K+, then this whole setup is pretty overkill.