I built a DIY rack (maple/brass) that was fun, but not cheap. Since then, I've learned some things from experience about certain downsides. The rack is nice and high, so perfect for playing vinyl, as I don't have to bend over. Luckily, all the shelves can be adjusted and/or removed, so I'm going to remove my mono blocks from the bottom shelf and put them on the floor. The reason, is to remove a layer of shelves so that I can lower the height of my rack, and I will then have to bend over. Huh?
The rack is in the middle between my speakers, so it and the equipment are interacting with the sound through reflection. By lowering the rack considerably, the sound will be truer and it will add stabilization, as I too have wood suspended floors.
What I have actually found to work for mechanical feedback issues through floors, are springs. I have spring loaded feet under my turntable and under my subs. I will probably keep applying these springs to my amplification. There are some in this Forum who build their own DIY spring solutions, plus I use Townshend Isolation Bars under my subs (not cheap).
When deciding on a rack that has to be placed on wood floors, it needs to be rock solid and handle feedback for the best sound (IMO).
Kenny