The quad core i7 iMacs (21.5 and 27) will run all of that brilliantly. Heck even the i5's might just run it all very well too. The need for a Mac Pro is smaller then ever now cause of how good the iMacs are these days.
I think:
High amounts of RAM (over 32GB cause the iMac can to that though it's expensive, but 16GB should run all of that just fine)
TBs and TBs of internal storage
User upgradability beyond RAM and hard drive
A need for more then 4 physical cores (though hardly any apps are optimised for more then 4 cores)
Are the only reasons to get a Mac Pro these days. If it's just to run the above mentioned apps then an i5/i7 iMac will suffice very well.
And I believe this fact alone is why the Mac Pro is not as popular anymore.
Theres more to it than that. Dont forget, not everybody is satisfied with Apples decision of the glossy screens in the iMac. Personally, the reflections would annoy the heck out of me and interfere significantly when Im doing colour sensitive work (75% of the time). Especially if the theme is a dark one and the person sat behind me, back to back, has his screen filled with bright content. No, let me choose the display I want to hook up myself. Besides, what happens if your screen dies on you..? Youve just lost your computer for a few days whilst it is being repaired. Down time like that is often not an option for a Pro working under a tight deadline.
In addition, the Mac Pros are much easier to gain internal access to. Just pop the lid and youre there. You can even do this as the machine is running (admittedly I cant think of a reason why you would

). The ability to very quickly swap in and out a set of HDs (in addition to the Ram and the Super-drives) without having to dismantle half the machine is certainly worth pointing out. Youre essentially back up and running much faster after hardware maintenance, upgrades, what have you.
Mac Pros also operate more quietly than any other Mac out there when placed under full load for extensive periods. Quite a boon in a quiet studio environment. Its one of the things I love most about my Mac Pro.
Also, being able to place more than one video card can offer up several key advantages. I know of one CG-artist who has two cards in his 2010 Mac Pro. One to dedicated entirely to GPU renderers like Octane, and the other to run everything else (OSX, other apps, etc.)
As good as the i7/i5 line of CPUs are, its my understanding that you cannot run them in a dual CPU configuration. That effectively cuts in half (give or take) their speed potential compared to the Mac Pros Xeons. Yes, my software is multi-threaded and will gobble up every core I throw at it. An i7 would thus, effectively, slow me down. They would certainly not suffice.
So as you see, the Mac Pros are really exactly that
.. Designed and built to cater to a professionals needs.
Dont get me wrong, I love the iMacs. Theyre brilliant machines. But for what I do for a living they are behind the Mac Pros on my shopping list and will be for as long as Apple continues to support the Pros.