What made you think I was not shooting in RAW + Adobe RGB but JPG + Adobe RGB? Which I'm not. But if I was then....?
Because you said you are shooting in AdobeRGB. If you are shooting in RAW, you are not shooting in a color space at all. The adobeRGB setting on the camera only affects Jpegs. Just because you choose to have the camera render an 8bit AdobeRGB jpg along with storing the raw data while you shoot doesn't mean you are shooting in AdobeRGB. And if you were then ... you're pretty much stuck with what the camera firmware decided to do with your raw data, since most of the data no longer exists. meaning post processing will be a crap shoot at best.
And if the iMac is a "limited gamut" monitor how is it you're able to get a "decent match" with your printer? Also if it IS possible to get a "decent match" then what is the point of buying a wide gamut monitor (e.g. one that can do "97% of the Adobe RGB color space, 100+ % of the sRGB color space...etc.")? Why make them? Why not just make monitors that can't do 100% sRGB like the ones in the iMacs? Why shoot in Adobe RGB/RAW then if they monitor can't even display full sRGB (unless all you plan to do is post photos on the web and share with friends via email)?
All monitors, even the high end ones are gamut limited. Your 7900 printer exceeds adobeRGB in many colors. If you don't want to limit the colors to your output device, you would need to work in 16bit/ProPhotoRGB (or just use lightroom which is it's built workflow). But then what do you do? Even a monitor that approaches AdobeRGB can't show you all the colors your printer can print.
You don't need to "see" a color on the screen to be able to judge how it will "look" once printed. You don't see an image in AdobeRGB, or ProPhotoRGB for that matter. You see the color in the monitors color space. Those colors have been modified by the color management system to simulate the visual relationships that we expect to see. When you print the image, they will be modified to that devices color space, and in fact take advantage of the gamut of that space. Making the mistake that AdobeRGB is a magical space that you capture, see, and print is a wrong understanding of color management.
I have a 27" iMac and numerous printers, including a 3800, 3880, 7900, 11880. The screen match is no problem. I also have setup a couple of Eizo's, Apple's 24" LED, and various other monitors. All work fine if profiled correctly. The 27" iMac exceeds sRGB in every color. No, it isn't as wide gamut as others, but the results on paper should not be hampered.
Here's a couple of graphs showing the 7900 against AdobeRGB. Considering that monitors can't show theses colors either, does that mean you just want to clip them with your workflow? Color management just doesn't work that way - in fact this is the very problem it has been engineered to overcome.
(wireframe adobeRGB, solid Epson 7900 on Epson Exhibition Fiber paper)