For $300 to $400 budget, the best choice is of course the AMD Ryzen 7 7800X3D.
DDR5 6400 CL30 is the sweet spot for Ryzen 9000 series.
According to latest rumors, Mac mini M4 will be much smaller than current M2.
I love hellhound from Powercolor.
1000W PSU is the ideal for this combo, and enough for future upgrade. For example Corsair RM1000e or RM1000x.
The 27" LG UltraGear 27GP950 is an excellent gaming monitor that supports 4K @ 120Hz with HDR and 10-bit color for Xbox Series X, lacking only Dolby V...
@Matthew0000 RM1000x is a very good PSU overall, I have it for several years, never has any problem.