I'm assuming you are familiar with Linux?
My personal opinion of linux is that it's an incomplete OS. People will surely disagree with that comment, but it's true. I've had loads of issues with various Unix OS's in the past, even with support from Hosting Companies.
I'd recommend Debian, if you are set on Unix, as my experience says it's the best out of the lot.
Although I'm a committed Windows guy myself, I'd highly recommend going Windows.
Problems are much easier to fix, and it's a lot more stable, much more user friendly, and has a built in desktop interface, so remote desktop access is no bother.
There are ways to get a free license, primarily if you are a student. Otherwise there is a free trial floating around (180 days I believe). Which is 6months roughly. Plenty time to decide whether it's right for you.
I doubt it's the servers issue and more a software issue (by your description). Not trying to dig at your knowledge here, but as I said before, Unix is an awful OS (why do you think it's free? :P)
If you are a student, check this out for a free Windows Server license:
https://www.dreamspark.com/Student/Default.aspx
P.S
Windows Server 2008 is better IMO.
AFAIK 2012 emulates Windows 8 Desktop. It's just more compatible to go 2008 atm anyway, since it's older.