Not long ago Microsoft decided to only sell licensing for 2012 Server, no more 2008; however one can down grade for free. Keys and ISO's for either operating system are available on Microsoft's eopen website.
Interestingly, there is no more Windows Enterprise, only Standard & DataCenter. So what happens if one needs to run Win2k8 Enterprise (because they have more than 32gb of ram or other requirements)? In the past one would have had to pay the upgrade price from Std. to Enterprise, but now all one needs to do is buy W2k12 Standard, and they have the option of down grading to 2008/2008r2 Std. or Enterprise! The ISO to download and the Key are exactly the same!
Small Business server also ceases to exists. SBS 2011 is the last version; it has been replaced by Windows Server 2012 Essentials (up to 25 users) & Foundation (up to 15 users). Windows Foundation does not support any sort of Virtulization.
Also some ram maximums/limitations:
Windows 8 supports 128gb ram; Pro. & Ent. support 512gb.
Windows Server 2012 Std, DC, Server Storage Std, MultiPoint Premium, Hyper Core all support 4Tb.
Windows Server 2012 Essentials supports 64gb.
Windows Server 2012 Server Storage Workd group, MultiPoint Std., Foundations supports 32gb.