That would be an excellent PC but get them to put in a 80-plus Gold PSU from a reputable brand like Corsair/Seasonic etc.
I have a 5800x and its a great cpu but you may want to consider a 12700k system , not sure what that adds uptoi with OCUK prebuilds, or even get them to put in a 5800X3D. If the pc is primarily going to be for gaming then the X3D is an outstanding choice for a large selection of games.
The other potentially controversial choice is the 6900xt. It is currently incredible value for that amount of performance but you will be losing out on raytracing performance. That is the only downside and it is a very good pick for 3440x1440monitor.
Oh and timing plays a part as well. By the time you actually get that PC from OCUK AM5 may have been fully anounced and your system will be a generation old. If you need a PC then you need a PC, never a perfect time to buy.
Edit - Get 32gb 3600mhz ram , DDR4 is so cheap you may as well.