There are three approaches we can evaluate here, maybe 4
For the sake of stating the obvious the I assume no keyboard, no mouse, no screen needed in this.
1) We buy all the same parts again and see what it runs. Risks both upgrade lockout if newer gear is there and one or whatever of those parts getting overpriced because it is an upgrade for someone/because it found some life somewhere. For instance I am not sure how valuable it would be to have a 1TB storage drive these days, and that motherboard will .
2) With the same money we see what we can get on the newer end of things, a lot of this is several years old now so things will likely have surpassed it.
3) Other second hand prices for things, be it whole machines or new. Also have the option to buy a non gaming machine and make it gaming one aka put a graphics card in.
4) Prebuilt machines, sadly they are mostly junk or massively overpriced these days (back when you could find some decent enough stuff for barely anything over parts cost, sometimes still less than pirating windows). To that end technically an option but the gun to head one for me as making a PC is easy.
Start with the motherboard
LGA 1151 Intel, 6th and 7th gen, max i7 (we are now looking at 12th gen, to say nothing of AMD actually coming out swinging and doing all sorts of good stuff)
DDR4 2400 max and two slots.
Mini-ITX so no surprise it is 1 PCIe slot
Has m2 and 4 sata which is not the worst.
Case is also miniITX which is nice. Should be on the smaller side then, not my thing (I would want more hard drives and more expansion, and more cooling) and I would not pay anything extra for it but some like the form factor. I will however note that it is losing support somewhat (not as bad as some custom things people did but I note it) so how long you will be able to keep that up for I don't know.
The Intel I7 7700 is probably the best of its generation for raw power. I would not look to alter this much but there could be some things depending upon how you want to roll. Also means comparing parts prices for second hand things is dubious here as it will be the upgrade path for many and thus commands that little bit higher as they know they will pay for it vs building a whole new machine.
16 gigs of RAM is fine. The utility of going higher is minimal from where I sit for most purposes and your clocks are max for the board, though very much on the lower end of what is available these days. I can't be bothered to look up timings as they rarely matter for anything other than the most pointless of benchmarks.
For the most part I don't care about coolers as they are there and working, and if it is water cooling that opens up another can of worms (sealed makes me worry about leaks, unsealed is tedious to handle).
PSU is a reasonable one as well from what I can see.
Graphics card was a pretty reasonable one some 3-5 years ago. https://www.asus.com/uk/Motherboards-Components/Graphics-Cards/Dual/DUAL-GTX1060-6G/
https://www.game-debate.com/hardware/index.php?gid=3671&graphics=GeForce GTX 1060 Asus Dual OC 6GB
https://www.game-debate.com/hardwar...GTX 1060 Asus ROG Strix Gaming OC 6GB Edition
Should do OK at 1080p/1440p. No chance of anything real in the VR world (I know the GPU maker claims it will but in reality it won't do more than middle of the road tech demos from the same year it was launched) or 4k world, and for some things you will have to drop settings.
I am not sure what that 500gig kingston is, and very curious why it is not listed when they were bored enough to note the power supply and extra case fans. If it is m2 that is something, if it is the last of their sata efforts then... eh.
1TB hard drive I use as a doorstop, though 2.5 I might save for a laptop. If it is mini ITX then do note that upgrading might see you have to find another 2.5 one (though most SSDs will be this I guess).
Second hand what could I do for $800 (popular price target for builds, https://www.wepc.com/builds/best-gaming-pc-under-800/
seems a reasonable intro to the concept in current times) at this point... harder as supply issues make things fun. You could probably beat this, and certainly have an upgrade path worth speaking of, even more so if you are willing to get by with a cheaper graphics card/onboard stuff for a while as you save up some more or go second hand (Christmas is in a few weeks so second hand tat sellers will probably be filled the day after).