I would skip the 2X TC. The 80-400mm isn't very fast and when you lose 2 stops with the TC it gets really slow. If you are shooting anything that moves, you will have a problem. Plus, I think you lose the VR feature, so it's like 2 stops of light and four stops of camera shake.
This is why I recommended the VR 80-400 over the 80-200mm with 2xTC
I am not sure about the 2x teleconverter but as far as I know Nikon 1.7x teleconverter will allow the VR and AF function to work on the 70-200VR.
Over at Dpreview and Nikonians, there are endless debates between 80-400VR vs 70-200 VR with teleconverter. 80-400VR has an older version of VR and is compatible only with handheld mode and not when on monopod or tripod.
The only real benefit of 80-400VR that I can see is the ability to add teleconverter to it for even further reach but only with MF.
Quality of lens wise, at 70-200mm range, the 80-400mm certainly can't quite compete with the 70-200 as far as sharpness go but I am not sure how much teleconverter will degrade the image quality at longer reach but there are many fine sample of 70-200VR with teleconverter on dpreview and nikonians.