This is goodbye

The Canon's sensor has sucha poor Dynamic range - you get horrible pattern noise that doesn;t clean well if you push file even just a stop. 
I replaced my 5DMKII with A900 - yes a bit noiser in the beginning, but you could push it really far with random noise pattern it cleans much better than canon.

5n, 5r and 6 are so good with noise (shooting RAW) - you should check it out.