I think the main question is about operating system. Nowaday servers are optimized for virtualization and, if you don't use an hypervisor, you will need a server OS, mainly because it is not guaranteed that Win10 will support all the peripherals.
If you do have a virtual infrastructure, go for it; you can easily get a barely used server with two hexacore Xeons and 192 GB RAM for less than 1500 euros. If not, you can try the VMWare ESXi free edition, now (if I remember correctly) there is only a limitation in 2 physical CPU (not cores).
I use IBM at work, but HW brand is not so important nowaday unless you need assistance.
If you are thinking about servers as slaves, I'd rather go for 2 slaves with less ram due to processor speed (so, two twin systems with 2x X5690 Six Core 3.46 GHz and 128GB RAM would be about 2100 euros...).