Just some thoughts:

Fans (of good quality) typically don't have much moving mass. Also, the vibration is parallel to the surface you mount it to, which means that a fan mount would always be better because mounts are much more flexible parallel to the surface than gaskets. Gaskets are pliable at right angles to the surface, but parallel to the surface they aren't (as much). I think it could be worthwhile on a power supply, because the fan vibration is at right angles to the mounting surface (with a bottom fan). With a back fan there would probably be less benefit. You would do better to replace the fan in the power supply if it was vibrating (and you are brave), but a gasket would be a cheap and easy quick-fix.

This is also why hard drive vibration is hard to get rid of in cases like the SLK3700-BQE. In the direction of the vibration, the only padding is the part of the grommet between the screw shaft and the edges of the hole it goes through. The supplied black grommets are relatively useless in this regard. When placed on foam or sorbothane, the drive is at some distance above the mounting surface, and the material is more pliable. I used earplugs rather, they turned out to be pliable enough when used as grommets.

A computer case is relatively heavy when compared to the vibrating components in it. Case resonance usually comes from specific places, like the side-panels. Specialised case feet probably wouldn't make a great difference in most cases. They are probably something to get only if you notice a problem (vibration in the desk).

There is a quick and easy way to determine if your feet are not adequate: get a sheet of bubblewrap, fold it in half or so and place your PC case on it and see if there is an improvement in the vibration/resonance. If there is, you should get better feet. Test this when your CD/DVD drive spins up, perhaps it can help there.

I used four black rubber door stops in place of the original plastic ones on my Lian Li. £2.50 from B & Q ( a local hardware store in the UK).
I was getting some eheim pump vibration transmitted to the wooden floor, which was cured by the stops.

A comparison of Gaskets with cable ties instead of screws would be nice.

That's easy enough to try once you have bought a gasket. It's not a case where that knowledge would save you money.

Acousti Ultra-Soft Fan Mounts available now. Any sources (in particular the OEM model)?

QuietPC UK has them. Didn't find anything else, but check the web sites on the AcoustiProducts' "Where to Buy" list; that's how I found QuietPC. They don't list Singapore though...

Acousti Ultra-Soft Arrowhead Fan Mounts @ Quiet PC USA. Do they offer quantity discounts?

*** If you are a reseller or a system builder we have OEM Acousti Ultra-Soft Arrowhead Fan Mounts available in packs of 100! Contact us for more information. ***

Any chances of us end users obtaining the 100-pack fan mounts?

Question - with the Acousti mounts installed, how easy is it to remove the fan (without destroying them)?

I've uninstalled and reinstalled them at least three times without destroying them. Often what happened is that the heads were pulled through the case. I could see the heads snapping in a case with sharp screw holes, but so long as you're careful I don't think you have anything to worry about. Try releasing the corners one by one so that the fan is removed from the case without removing the grommets. Then, you can be more careful when the grommets are removed from the case.