If I had to buy a prebuilt today for that price I'd probably get this:

https://www.lenovo.com/us/en/p/desktops/legion-desktops/legion-t-series-towers/legion-tower-5-gen-8-(26l,-amd)/90ux0012us

In that range, you're looking at a 4070 for Nvidia.

If you look around you might get a better deal on something with a 6900 in it if you want to go AMD or maybe you can get lucky with a 7800xt.