Jolida Foz SS-X Tube buffer & soundstage expander?

I find the 20hz bass boost to be helpful and the image widening to be great for me, as in my office setup the speakers need to be a little closer together than would be optimal. One minor issue is that with my 91db-efficient speakers, I do hear an audible pop when switching the unit off. I do not judge this to be bad enough to be worrisome but it is definitely there. Easily remedied by turning the power amp off first.