PC Master Race

Today my PC finally ate it. No POST, no disk activity, so I'm pretty sure the mobo has failed. I built this PC 8 or 10 years ago, and I'm honestly too old and out of touch to know where to start on a rebuild lol.

I'm an arch Linux user, my job is in machine learning, and I'm looking at a soup to nuts style rebuild but I don't know where to start. I want as much future proofing as I can get and I'm happy with a budget anywhere from $2k to $8k. I don't game now, but I might want to in the future.

So it seems like to leverage good ML tools I'm locked to cuda, so probably Nvidia GPU. Does that mean 4070 Ti is the knee in the curve? CPU I came from AMD but I have no idea. RAM speed is something I have never ever considered. And mobo wise, I have a couple of M.2 drives now, but I'm not sure what else should drive decisions? 1 monitor currently that I intend to replace, so I'm not sure why I would need multiple GPUs or something that necessitates a lot of PCIe connections.

I want a plain old closed black case, no color changing gamer shit, and about as much computing power as I can get. Pcpartpicker came up a little short, how do I start?

I've got maybe a week of lead time, then I would like to pull the trigger. This whole build process was a lot easier circa 2003!