Don't get a used gpu. Now days the used ones are possible used for gpu computing. Overclocking 24/7 operations can result in not so good shape.
Most computer parts I would not recommend getting used. I've done it before and isnt bad. Im just saying not recommended.
If a used system is purchased then buy a new gpu at the least. ( see benchmark link to find a good deal below)
threadripper are not bad but not so much for longterm. Life expectancy of intel are expected to be greater. That is why they typically cost more.
be smart do your research and plan ahead going with 2066
GPU for gaming ( can always be upgraded) spending less on this now isnt a bad idea if you have to. You can always upgrade the gpu.
The harddrive isnt very important. You can always get a disk drive now and upgrade to ssd later.
The CPU and motherboard lifespan are based on socket type. I speculate the LGA 1151 will not be supported for to much longer.(even though they are some of the current top bench-marking cpus) This is why I am moving to 2066. If uyou can afford a 2066 build then absolutely do that.
I will get myself a low end cpu for now and upgrade next year.
The most important thing is the motherboard. This is what will determine how much and how long upgrades can be made.
Currently the most recent socket type for intel is the lga2066. I would expect top bench-marking for approximately 4 years on them.
Here are benchmark stats if you are unaware of them. GPU and CPU listed.
https://www.cpubenchmark.net/high_end_cpus.htmlhttps://www.videocardbenchmark.net/high_end_gpus.htmla solid affordable high end 1151 system can be build.
Keep in mind that $1000 spend on 1151 cpu and motherboard will not turn out in 5 years. The system will likely be outdated with limited cpu upgrade potential.
I personally thing they will still be solid systems but after 6 years or so they will not be mid performance systems.
While the 2066 systems will still be manufactured or at the near end of there lifespans depending on evolution of systems and tech.
I dont think any of us could predict the future evolution of tech ( it can be a wild thing) but 2066 are newest and will stand for a while unless something wild is invented.
There are many limitations that impact the progress of cpu development.
Here is some insite about intels design and architecture.
Skylake, Kaby Lake and Coffee Lake are the current architectures for consumers.
Upcoming architecture is Whiskey Lake and Ice Lake.
https://en.wikipedia.org/wiki/Ice_Lake_(microarchitecture)https://en.wikipedia.org/wiki/Whiskey_Lake_(microarchitecture)https://en.wikipedia.org/wiki/Coffee_Lakehttps://en.wikipedia.org/wiki/Skylake_(microarchitecture)https://en.wikipedia.org/wiki/Kaby_Lake