For a system tailored for dealing with GIS data, you usually need a few things:

A powerful processor (say, a 13900k or 14700k, if intel, or a 7950X3D if AMD)
Ample RAM (32 GB minimum - if you're running a lot of background processes, then 64 GB)
A dedicated graphics card (RTX 4070 or better)
A solid-state drive (SSD - 3-4 TB)

If you're balancing cost and performance in a new build, with the intention of getting something powerful and won't break the bank, you'll want at a minimum 32 GB of RAM and at least 2 TB of SDD storage (ideally, you'd have 4 TB or more, given you do mention large amounts of data).

With regard to processor, it depends on a few things - since you're mentioning a desktop and that cost is an issue, you probably aren't looking for something like a Threadripper. You still want something relatively high power though - so like a 13900k or 14700k, if Intel, or 7950X3D if AMD). Be aware that if you're going for Intel, anything beyond 14th Gen will be using a new socket, so there's no easy upgrade path without getting a new motherboard, while the next generation of AMD will continue to use the current AM5 socket.

Finally, for your GPUs, you probably want to choose a model which supports deep learning and spatial analysis, which probably means something like a GeForce RTX 4070 SUPER 12GB or better. You can of course get something more powerful/pricey, like a workstation GPU, but that might rather affect your cost vs performance.

Best specs for GIS?