At that price point, I would stay out of the extreme territory. I would stick with a Core i5/i7 "K" on an Intel Z97, a good air cooler for some overclocking (or a self-contained loop water cooler if you're feeling frisky), 16+ GB of memory, a 500GB or larger SSD for OS/installations and a hard drive of some kind for bulk storage. I'd go with a single nVidia 980/980Ti. That all should bring you pretty close to $1800.
For the above specs, a 750w or so PSU is enough.
16+ GB of memory is overkill, but your budget for a "2nd machine" is pretty huge so fuck it.
2015 is going to be a big year for SSD technology, so standard SATA3 SSD's are getting really cheap right now. M.2 and NVMe will be emerging this year but SATA3 SSD's are still plenty fast and for the price, can be huge bargains.
If you wanted to spend more and go pretty extreme, you could consider one of the LGA2011 6- or 8-core Intel CPU's along with DDR4 memory and/or SLI/Crossfire, but this is a 2nd machine so. If you went that route, you'd probably want closer to a 1kw PSU instead.
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