geofelt :
Prioritize your needs.
I might consider the new monitor and desk first.
PC components keep getting better price/performance over time.
Some components are timeless and could be bought early if you see a good sale.
That might include a PSU.
Buy the case and cooler together, you need to know the case specs to properly fit a cooler.
Early, on sale is ok since they do not change much.
Buy the cpu/motherboard and ram together; they need to be compatible.
I agree, there are some components that HAVE to be bought together, like CPU,motherboard, and ram. Cases and coolers, if you indeed need an aftermarket cooler. Other components can be bought individually on an as funds are available basis, such as Monitors, keyboards, mice, gaming controllers, anything considered a 'peripheral',
I would probably recommend getting the PSU when I got the case, but that is a personal preference.
As your graphics card and CPU are still relatively strong, I would definitely look at getting the monitor and desk first.