Those look great

!
I have been a fan of the Vulkan Battlesuits since I first saw them. You have really done them justice. I have never really liked the exposed head on them though...
Funnily enough, I have 3 on my workbench at the moment, getting their final lick of paint. I have filled in the head area and added a screen instead. If you are interested here's a pic of how I convert the head area (this one has a few added bits and pieces too):
I can't wait to see your weapon arm conversions. Are you going for a PaK cannon look or something similar/different?