Knowing that you're sitting below the perf/$ curve with past gen hardware, it all boils down to cost. And that's certainly not a black-and-white metric.
Generally people's "hobby" time is highly variable also depending on their work & family load, but generally pretty worthless. Hobby hours can range from 0$/hr to Jeremy's $150/hr, or more. That's something every individual needs to measure personally. Perhaps more importantly here is the potential for downtime. If this is a mission-critical (business-use) machine, then less downtime is better. If it's a personal/gaming machine, you can probably get away with even a week or 2 of downtime (depending on your gaming addiction withdrawals).
I recently did a CPU+mobo+RAM+SSD replacement, and actually assembled the new bits outside my case with a spare PSU (GPU if needed) to get everything (OS & software) set up before I made the physical switch. Minimizing downtime to the 2-3 hours it took me to disassemble my old system from my case and install the new bits.
My additional thoughts on your scenario:
- Ryzen 3000 series will provide a much-needed uplift in per-core performance compared to your 1700X.
- New Ryzen 3000 CPUs are more expensive than their performance reflects. Especially when you have things like the Ryzen 5500 for $140 on the market.
- You'll have to decide whether you can give up a couple cores for a cheaper 3600/3600X or if a 3700X/3800X is required for the 8C/16T.
- Buying a new motherboard just to support a current-gen CPU opens up a whole can of upgrading worms. Replace/upgrade the existing RAM? Since you'll [assumedly] be reformatting at that point, time for a higher capacity SSD? It also means you're going to strip everything out of your case and re-assemble, as opposed to popping off the CPU cooler and swapping in a CPU. Downtime = see above.
- If you end up with Ryzen 5000 system, that's 1.5 years old now and due for a pretty significant replacement with Ryzen 7000 this fall alongside AM5 which will assumedly have at least an additional generation of CPUs to upgrade to past the 7000 series. Yes, there's always something newer/better/faster on the horizon.
- On the DDR5 premium. Maybe easier to consider this less as +$$$ and more of a percentage of the build cost. An extra $100 on RAM sounds like a lot, but if it's only 10% more cost in a $1,000 upgrade....meh?