Actually, Windows 7 and Server 2008/Server 2008 R2 are generally compatible with each other. So, no, don't install Server 2012 expecting it to be compatible, as you may be disappointed; it's Server 2008/2008 R2 you're looking for here.
So, I'd install Server 2008 R2 in whatever edition you need, and frankly, do everything I could to avoid Server 2003, even as a Hyper-V VM.
Also, I'd advise avoiding Server 2012 and Windows 8 until SP1, particularly if this is in a professional (production) environment. You need time to get familiar with the new platform, and waiting for the first major service pack also gives Microsoft time to fix the bugs and issues found by all the early adopters.
Don't get me wrong, I've got lots of it around in test and training environments, but I'm not about to put any actual business systems on it until it's mature enough, and I'm familiar enough with it that it's not begging for a catastrophe to do so.