.. and I'm lovin' my camera - whatever number is on it - as long as it let me shoot photos like this
GET OUT AND TAKE SOME PICTURES!!!!!
The worst picture is the one you never took. Seriously, you are not talking about that big a difference for snapshot sized prints, 300 dpi x 8 x 10 = 5.4 MP, video is worse (HD is 2 MP, computer screens are smaller) -- You Can't Even View Anything In 18MP!!!!! How Do You know what quality you have right now?
We used to have this problem in computers, people would constantly be waiting for the next big thing and not buying one yet -- not understanding that economic thing called "opportunity cost - what it costs you not to be taking pictures now.
Sure the 5D2 is better and the 5Diii even better and the 1DS IV even better and the 1DX even better and .....; this is called Grass is Greener syndrome -- you have nothing to judge by
And let me add this word of warning - never buy so much camera that you can't afford to replace it when broken / goes for a swim / gets stolen / migrates away for the winter (likely with a so-called friend). It sounds like a 5 D III is that kind of camera to you
My suggestion is to get good and used to the 60d's quality, look for rentals on a 5 D II (to use as a primary body keeping the 60d as a second body) and see if it is worth the money FOR YOUR USAGE! This is not anybody else's camera, it is yours. Many other people here are speaking to their usage, their needs (or worse, just plain snobbery) and don;'t know, can;'t know your needs and usage
I am confused about your need for higher ISO - there is no magic wand, the 5D III is better at noise reduction (making a higher USABLE ISO), but really significantly so? For your expressed need "for shooting f/4 with the 8-15mm Fisheye, as I prefer to shooting during the blue hour(s), and also at night. As well, what meaning has it to get a 8-15mm on a crop?" -- never heard of a tripod (remember the triangle ISO replaces Stutter speed replaces aperture replaces ISO .....)? Ever hear of Lightroom? Photoshop? ways to do this ... what have you tried?
When all has been tried (which you need to learn anyways if you are using a more expensive camera); then consider the new expensive rolls-royce priced camera
It's your money you are wasting
It's good to know that some publications are using good photographers, instead of trying to pay peanuts on microstock sites to get the images they are looking for or paying someone with little or no experience.