Snaxo placement is indeed rather critical in an Active system.
I've found placing it as far from large power transformers as possible and on its own shelf to be very worthwhile.
In my case it is a tall-level Fraim atop my three NAP500 DR Amps stack. You may also find that position on the shelf itself quite important to get the best performance; in my case somewhere near the middle works best and it is rather obvious to locate the right spot as the sound snaps into place when it is correct.
Also the Supercap supply for the Snaxo location is important to get right. Give it some space from other large transformers in other supplies and the sound will open-out better - I use a Medium level to give more space from the nearest 500PS unit and that is very worthwhile; on a medium level it is more murky.
Experiment is best. The 'floaty' BMR snaxo box benefits from being on a heavy stack with its own shelf, whereas I found the non-floaty ones preferred a lighter stack or their own light shelf. I think this down to what stack resonances the sub-chassis better works with.
All this was an annoying discovery several years back, but if you get it right then the Active performance can surprise you. 
DB.