For sure, I'm mostly looking for ideas. Should I go for Broadwell-E 6800K? Or try to find a cheap 5820K? Performance/Dollar should probably be my goal.
I can see "where you're comin' from" with this: your hardware inventory and enthusiast profile are in my own cohort.
This current rig I'm building -- Z170 and i7-6700K -- is a realization of three "plans" I developed over a two-year period. First, I was going to build an X79 system with an Ivy Bridge E CPU. Then Haswell came, and I waited. Next, I was thinking about a Haswell-E. It came, it went, as I waited. Finally, I came to the conclusion that a quad-core K processor filled all my real needs -- the rest would simply be "collector's satisfaction," bragging rights and an over-investment.
But if someone gave me a perfectly good X99 board, well -- I'd have to fill it with a processor and RAM. I wouldn't be able to help myself.
And I can't tell you which way to go between the 5820K or 6800K. But with the hardware collection I currently have, I might be tempted to settle for the Haswell-E. How you might incline might differ.