Does highend heavy amps needs ampstands?

putting it on spikes (tiptoes) with protective discs for the floor should do a good job. If your amp weighs over 50 pounds that should do enough. A block of granite or other stone or concrete would be good too. A stand if you are loaded with $$$.
Yes the amp should be isolated from the vibratioal feedback of the floor. a lot of electronic parts can have effects from being vibrated, the biggest is tubes, but caps and other stuff can add grung to the sound from being vibrated.

Elizabeth, have you anything to back up your assertions about the ill effects of vibration on solid state circuitry or are you repeating something someone repeated to you because that person had heard it also repeated. I think I am being repetitious, you get my drift.

All amps especially powerfull ones do have a vibrations and you can't kill it whether you're going to use granite or marble stand.
Elevating the amps will add an extra room for heat sinks. I have my amps on my journal table since I needn't any journal table now and it kind-of convenient to access to the binding posts, mut switches etc.