There have been a few threads in the PA forums about what people are using, but those discussions are rather close to the boundaries of the NDA that players agreed to. And practically speaking, the ongoing development has been improving the game performance for most PA testers on a regular basis. So it's hard to have a meaningful discussion about what a 'minimum' spec is, or what level is needed to run everything at 100% and still get good framerates.
If you don't get a lot of response here, I'm pretty sure that there will be much more discussion on this topic after Alpha opens. And you'll still have plenty of time to research and shop for deals before Beta or release.
My current gaming rig is a desktop. Everything is at factory settings, no overclocking.
I've been building my own computers for about 20 years. The current one has a mix of parts from previous builds. The oldest part of the system is a big server case that has lots of room for upgrading (and airflow), 6 exhaust fans, and is at least 10 years old. The power supply & MOBO were bought 5-6 years ago, with a slower CPU and only 16 gigs of RAM - leaving me room to upgrade later as needed. I bought the CPU new just a year ago, but it is a 4th generation Intel that was first released around 2013. (I believe Intel is up to their 13th generation currently LoL) I got the screen nearly 2 years ago when my old one died.
When I got into PA testing in Jan I needed to buy a new graphics card because my old one only supported DirectX 10 and DX 11 is the minimum required to run Pantheon. That's my newest component. I was short on cash and $250 US was all I could spare at the time. For the money, I've been quite happy with the RX600 though. From as low as 30 fps to as high as 80 fps playing in PA, there's no obvious change on my screen. The game runs smooth and steady. No tearing or hitching. I attribute that to the Freesync system that matches the refresh rate of the screen to the frame rate of the game. Of course nVidia has their own version that likely works as well. I wouldn't buy any card without that feature.
I'm saving up to buy a more powerful card when the game releases. My monitoring software tells me that while the graphics card is usually running at 95% utilization or more, the rest of my system is loafing along at about 40%. Which leaves me confident that the rest of my system can support a significantly faster card. So that's pretty much the only upgrade I plan for Pantheon.
I think I'll be quite happy with this system playing Panth. However I'm also not hung up about having absolutely 100% maxed out graphics all the time, everywhere. I'm sure I'll be able to hit 80-90% most of the time, but if I have to back it off a bit for the most intense situations I'm not going to be concerned. I've lived long enough to learn to be happy with a reasonably successful outcome and not stress out about failing to achieve perfection.