Thanks. As long as the clock speed difference does not translate into a big performance difference then the 2.3GHz is what I should be looking at as the basis of my calculation. Add to ebay price the cost of maxing RAM plus adding 256GB SSD. If it's close to similarly appointed 2.6Ghz or loaded 2.3Ghz, then buy higher end; else buy lower end and do upgrade myself.
One thing is for sure: I'm getting pretty burned sifting through ebay listings. Happens every time. This thing must end! ; )
I am of the view that you should include the 2011 server model in your search if.. and it's a significant *if* ... if you don't expect to need the faster speed of the USB 3.0 ports. which usually translates to - "Am I going to be using an an external USB hard drive a lot?".
The 2011 server is a Sandy Bridge quad core CPU - which is a huge jump from the Core 2 Duos in the 2010s and similar IPC (performance) to the Ivy Bridge CPUs in the 2012s. It will turbo up to 2.9Ghz under load (vs 3.3 for the 2.3/3.3 for the 2012), and get the job done.
The integrated graphics in the 2011 (HD 3000) are fine, unless you are playing games or doing 3D graphics - in which chase the 2012s have around twice the 3D graphics performance of the 2011 quad core. Anything 2D, or video playback should be just fine.
Having done some heavy duty software development on the mac, I can attest that for some situations the quad core really makes a huge difference (like when I would have multiple things running at one - server instance, xcode, iOS simulator, etc), and it sounds you are using a commercial software package which has multiple components running at the same time.
anyway, that's my 2 cents.