You really should stick to just 6 cards, any more and you will run into stability issues. Compound that with the fact that for some reason you are running windows to mine with and you will end up with a rig you have to mess with every couple of days.
I agree. However for me stability for each rig is variable and to be tested. I have experience for a few rigs that run smoothly with 8 GPU but they are on Asus mobo (which known for stability!) MSI often gives me this kind of head ache, I will try to make this work and let's see how smooth it can run.
And of course i prioritize stability, if it's not stable it sure is not worth the effort and time, in that case I would stay with 6 cards