Thanks for the reply curegeorg. Just to clarify my first post, instead of saying “unstable”, I should have said “tippy”. I’m more concerned about the whole unit tipping over then I am about its weight capacity. Of course if you push on the top of the unit it surely would tip over but I guess I’m just wondering if it would be within reason. The 2 add on shelves I’m referring to would be the ones listed under the accessories. Would the unit with 6 shelves be less tippy if I used the adjustable feet instead of purchasing casters for it or would it still be ok with the casters? I do own the much wider video rack with 4 shelves that I use in another room with a 36” tube tv and a large Yamaha receiver among other components. I really like it but I don’t have the width to use the video rack in my living room, but instead was hoping to use the audio rack with a width of just 23”. Also I was wondering why the top monoblock would need so much space for cooling when the other monoblocks stacked below it only have maybe a ¼” of clearance and they are supposedly fine with cooling? Does more heat collect above the top unit somehow? Would small fans be a good idea? Thanks again.