You want to run a server, so you want good power efficiency and stability and overclocking is doing the opposite. 3200MHz is the fastest that isn't overclocked. More important than the speed is the stability and data integretiy of the RAM and that you notice it when the RAM is failing and destroying all your data on the SSDs. Thats why nearly all servers use ECC RAM.
By the way...the 3700X got no iGPU so you want to buy atleast one GPU.
Best would be if you read a little bit about virtualization, PCI passthrough, ECC RAM, raid, bit rot, ZFS, sync and async writes, write amplification, redundancy, snapshots, backup strategies and so on before buying stuff. Building a server is different than builder a gaming PC. You got other workloads and that may require other components.
Lets say for example you want a Win10 VM for browsing or office work. Without a second graphics card that you PCI passthrough to a single VM your Win10 probably isn't able to playback simple stuff like a youtube videos. As soon as you virtualize a OS you can't use your hosts hardware anymore. Because of that the hosts GPU can't be used, the VM is missing hardware accelerated videa decoding and video playback is done in software by the CPU. Then your CPU is at 100% utilization just for playing back one video and maybe it even isn't fast enough for that so everything is stuttering.
And lets say you want to virtualize three Win10 VM. Know you need 4 graphic cards because you can only passthrough stuff to a single VM so every VM needs its own GPU.
Similar problem with network cards. You can use semi-virtualized NICs so multiple VMs can use the same physical NIC but for that it isn't recommended to use hardware offloading. And if you disable hardware offloading your CPU needs to do many of the stuff the NIC would normally do. So many people buy NICs that allow SR-IOV so you can PCI passthrough virtual functions to different VMs to get way better performance and less CPU usage.
And if you run several VMs you get alot of more IOPS, because more stuff is done in parallel. And maybe you want your data to be safe and therefore you might want to use some copy-on-write filesystems like ZFS with checksumming and raid that can auto repair corrupted data. That together with virtualization and sync writes causes alot of write amplification. For example for every 1GB written inside the VM 30GB are written to the SSD. That way it is easy to kill a consumer SSD within weeks or months depending on the workload. And if the SSD got no powerloss protection it can't cache sync writes and if it can't cache sync writes your SQL DB will be super slow.
There is alot of stuff you might not think of when building your first server...
A second hand server might also be a good choice. For 400-500£ you get a complete 12 core 24 thread server with 128GB ECC RAM, three real 16x PCIe + three real 8x PCIe slots, 4x Gbit Ethernet or even 2x 10Gbit Ethernet and alot of enterprise features that a gaming PC is missing. If it is that cheap it is a older one. But if I want to pull a heavy trailer 24/7 I would rather buy a old but strong and reliable truck than a new fast sports car. Right now you are building a fancy looking sports car.
