In most cases, not terribly, unless the components on it are VERY poorly designed. For a turntable, on the other hand, pretty darned important.
If you are going to worry about the effect of small vibrations on electronics, and i wouldn't, you should be even more worried about where you place whatever rack you use. Is it directly impacted by speakers' bass? Your dishwasher? The dog wrestling with your son? By the way, who bit who?
I digress.
Many people have a "wall-o-audio" with speakers on the sides and a stack of stuff between them. I don't. I do have my amp(s) between them, on solid stone slabs (bunch of reasons, few having to do with sound). On the other hand, my TT, CD transport, DAC, preamp and tuner - all of which one could argue are affected by vibrations, are way on the other end of the room, with long interconnect cables. if i'm not testing stuff (which is rare) they are balanced. This has a very large effect on vibrations - regardless of whether you decide that effect is audible. You might also place them on a solid (brick, stone) floor rather than a suspended wooden one. I don;t have that option.
In the end I'd put money into a better pair of speakers, DAC, or TT/tonearm/cart/amp/ preamp before I'd put it into cabinetry - unless you are doing it for aesthetic or convenience reasons. The results will simply be more compelling, unless you have that elusive "perfect" system. In that case, please invite me over.
I'll bring good wine, promise.
G