Do stands make a difference for equipment?

They do make a difference but I wouldn't buy one at the expense of other equipment. If you are still building your system, I would get a rack last.

Star Sound Audio Points under my gear and subs, and Sistrum Platform SP-101s under my main speakers has made a significant improvement in my system's sound: clarity, naturalness, and ease of flow of the music. Under my main speakers on my suspended hardwood floor I could see, but under my gear? I was/am astounded.

You have a very good system, well past the point where a good equipment stand would make an positive audible difference. I use the Adona Zero SR4 and love it. To me, it had the effect of making the speakers dissapear more as sound sources, which probably has to do with the added stability lowering noise maybe. Who cares why; it looks great, has great access, and is super stable. I too used a Target T5 for about 15 years. No comparison. Core designs makes well engineered racks that are very attractive as well, but use a good bit of wood if that's your preference. We all know some of these brands can reach very high prices, but these two brands are within reason. Another good thing about the Adona is the great and easy adjustability of the shelves.
Reading what Rockadanny said above reminds me about Starsound. If it within your budget, I'm sure ut is better than what I have. I have the SP-101 supports beneath my speakers, but if I could afford the equipment rack I would buy one. They are the real thing.

I nam sure they do, as long as you avoid glass shelves. I use a good quality, but not expensive wood stand and add decent footers, which can be a cheaper way to good isolation, but I am sure they make a difference.
I would say TT> tube amp or pre amp> speakers, in that order of sensitivity to isolation