Upload & Sell: Off
I understand your saying about the 2N, and maybe you suffer from the same constraints as i do.
I have the 5 and the 2N, they are not very different. The 5 has an advantage on resolution (i find it quite useful) and small advantage on noise performance at High ISO.
The problem with High ISO noise in any of them (more in the 2N) is poor light. A perfectly balanced with good light picture from the 2N, can be magnificent at 1600ISO. Same with the 5D, but it can go up to 3200 with good results.
My main issue is i only raise ISO when the light is weak and the lens is not fast enough. So my 1600 ISO pictures with any of them are 90% of the times, just so so. I use the MDP as you do, plus the 50 f1.4 when i have to.
I have a friend that shoots a 5D2, and he can get ISO 5000 pictures that look much better than my 1600 ones, mainly due to better exposure (more light sensitivity) and better high iso. This in the same poorly lit scenario.
So....just hold on for the 5D3....and buy a used 5D2