How important is the rack you use for your components

I’ve been browsing thru people’s systems on audiogon and have seen all different kinds of racks, shelves, bookcases , stands etc. For people’s equipment. My question is how important is the rack to the sound of the system. Has anyone gone from a basic rack to a premium and/or home constructed rack and noticed a marked improvement? And when I say marked, I mean marked. Looking for input