Industrial strength servers for heavy lifting!
First consider which is more important- SPEED or SPACE. SATA servers use spindle drives which read and write a bit slower, but provide massive space for your accounts. SSD servers use Solid State drives, which are lightning fast, provide instant restarts, but are limited in space.
Also, bBefore you purchase your dedicated server, consider the primary domain for that server. You will need to create nameservers such as ns1.yourdomain.com and ns2.yourdomain.com. When you point domains to hosting accounts on your server, you will use your custom nameservers.