I doubt he'll need a powerful CPU? I mean I have a 7700k and it still runs great for modern titles. Seem usage around 50-70 and temps at 43-50c. I'd go water-cooling with the extra money if you can. This could mean your brother will play with a water-cooling loop on his CPU which makes the temps low and he can probably overclock to 4.8-5.0GHz. GPUs are a little hard to get these days, the RTX 2000 series stocks should be back soon and should be enough. I hope this could help you out.