JR has been a Linux guy for about 20 years exclusively. He's building a new computer with a fixed budget. Leo recommends going to PC Perspective's website and on the menu bar they have the HWLeaderboard. The Hardware Leaderboard lays out price ranges for building your own PC and what components you should get.
If he sticks with Linux, the issue will be drivers. The good news is that Steam is using Linux for their Steam Machines and as such, Linux support is growing.