Advice needed for a new PC

[Stamper]

If you want not a laptop, but a tower, the best best is HP Elite 8300. A core i7 will come at around 300 bucks used.
Then you can upgrade the graphic card to any card with 2gb or 4gb ram, include a SSD, switch the DVD burner with a Blu-ray burner, then install OSX Sierra on it (takes about an hour) or dual with Win10 or 7 (usually 7 licence comes included with it, no need to ever enter the licence you just install and it works), this will make you a killer, future proof, 4K editing proof tower for less than 600 with all the additions, which you can swap at anytime.

Even upgrading the RAM up to 32gb is possible. A similar Macpro would cost you thirteen times the price! up to 10 000 to 12000 bucks for similar perf.

[Koopa Luath]

Wait a second, you can install macOS on a Wintel now?

ETA: How much processor capacity would be recommended for 4K processing, anyhow?

[spoRv]

How much processor capacity would be recommended for 4K processing, anyhow?

The more, the better... I would not attempt to use a laptop for "serious" 4K projects - as written in previous posts, it would "melt" sooner or later, as it should be left on for dozen hours, if not days! For desktops, my hints are the following

CPU: I'd go with a quad core "K" series, so if you would need to overclock, you could be able to do it... new, an i7 7700K, used an i7 4790K; not many softwares take advantage of multi core CPUs, so I don't know if a 6, 8, 10 cores would effectively be more powerful...
RAM: 2x8GB at least - so, if you want to upgrade, you can just add two more RAM sticks
HDDs: a small SSD for the OS, and huge mechanical hard disks - even low RPMs could do, and if you eventually need speed, you can use two or more in a RAID0 configuration
GPU: you should not need the most expensive one, just grab an high quality model
Cooling system: better to go with liquid ones
Other: consider internal audio and video capture cards could be found used at a very good price, and could help your restoration projects.

Hope this would be of some help.

[Koopa Luath]

It just might be. I don't suppose there'll be a laptop capable of editing in "serious" 4K projects with relatively little trouble for at least a few years--after all, the 4K market is only just starting to blossom.

[Stamper]

Yes, just see this thread here Apple are thieves. It's daylight robbery.

[Koopa Luath]

Well, now I know for sure 4K is out of my reach for the time being AT LEAST. Even if Pioneer's burner, the first of its kind, is here on the market, content providers have forced the 4K market into a very small corner of computers--nothing short of a Kaby Lake processor can do jack about 4K, plus there's AACS 2.0 (which is also preventing the major players in the ripping industry from supporting UHD in the first place), Intel's SGX, HDMI 2.0, HDCP 2.2... let's face it, we're SOL at present when it comes to 4K.

[Koopa Luath]

Since I'll be using DaVinci Resolve for manual color grading, I'm going to go for either a 1070 or a 1080 for the GPU. Any other specs to recommend for such a powerhouse editing suite, even a free one?

[Koopa Luath]

Also: would a CRT be useful as a second monitor for a BMD setup? Because I've got an old HP CRT that may be useful if a BMD setup for color grading could take a CRT.