First off, kudos for bringing him over to the light side! Now I found the ASUS GR8 II-T044Z through recommendations of PGR( https://www.progamerreview.com/best-pc-desktops/ ) and I have been really happy with it. It cost a little under 900 dollars and can run everything I personally play smoothly as silk.
Now, that being said. I don't play most fresh triple A games on my PC and mainly play Overwatch, Wow and heroes of the Storm(Yes I like blizzard). So I don't really test it too harsly, but if you want to play the latest AAA titles you prob need to spend more than 1k anyway if you want it to last.