The workstations that age well are rarely the ones with the most impressive launch-day spec sheet. They are the ones built around upgrade paths, honest power budgets and cooling that stays quiet under sustained load.
Spend where it compounds
GPU memory, system RAM and fast NVMe storage compound over the life of the machine. A mid-range GPU with generous memory often outlives a flagship with less, because the memory is what the workload outgrows first.
Plan the second upgrade
Choose a platform that accepts the next GPU generation without a full rebuild: a PSU with reserve capacity, a case with real airflow, a motherboard with the slots and lanes you will want later. The cheapest rebuild is the one you never have to do.