I guess you are coming from VMware setup.
Proxmox is different.
As it is a Linux based , and Debian to boot, it will and usually run on preaty much any hardware. It is hard to find machine that it will not run on.
That said ,however, a lot depends on your use needs/wants.
A simple virtualization setup , where you just want to run a number of VMs for various needs that do not require a hardware passthrough for video, audio, USB and disk controllers can run on anything.
Now when you do need any or all mentioned above use you need to do your research on MB and CPU capabilities like iommu or equevelant support this is must for passings controll to all of that hardware into VM. So it is up to your needs to figure out. Unlike VMware which is very much business oriented and thus controll what hardware it supports proxmox is rooted in lunix with all goodness of it.
It uses regular Linux kernel so many drivers is supported out of the bag. Many custom drivers are available from Debian site. Server market is sparce so you lost probably will not need custom or third party drivers. Also Dell and hp have a decent support for Linux as they do offer servers with Linux installed. So chances are all will work out of the box.
Just try it.
I run proxmox on 15yo supermicro and opteron for ages. I now run it on a 3 yo Intel based system from same mfg. With an HP disk controller.
You may need to flush your disk controller to it mode for better zfs experience. Or not.
