In order to go further regarding my machines and what I wanted to learn, I decided to by an entreprise grade rack server.
It's an HP Proliant DL180 G6. It initially came with 16GB of RAM, and I upgraded it to 48GB to make more virtual machines. It also has two Xeon CPUs and two power supplies. Inside there are 8 hard drives which have 500GB of capacity each. The RAID controller is an HP P410i Smart Array, which came with 256MB of cache, which I upgraded to 1GB. It has two network interfaces for failover, but I only use one as it is a home server. It can be configured via its BIOS and the RAID controller has an interface for managing volumes.
After having tested many virtualization solutions (Hyper-V, VMWare V-Sphere, Proxmox) I decided to stick with Proxmox. The main reason is that it is Linux-based and comes with a lot of utilities, and it is possible to make virtual machines and containers with it. The web interface is simple yet very efficient.
In Proxmox it is also easy to setup a cluster of servers, as everything is done through the web interface. For now I only use it to make virtual machines of operating systems I want to test, but I plan on learning more things that come with it, like CEPH for example, which is a storage cluster utility. Proxmox also supports RAM sharing between running virtual machines, which helped a lot when it only had 16GB of RAM.