I guess it didn't occur to me that speakers produce vibrations :P Such an obvious thing hehe. But yea, I have my power amp, monitor, DAC (no longer the D1) and 2 speakers on my desk as they all fit together nicely. Here's an old picture:
Now, the DAC sits on the power amp next to my monitor... Anyway, I personally don't notice any ill-effects. I mean, I have absolutely no noise at all, even cranking the volume.
I think any improvement from spikes on the D1 could be due to the tube or quite possibly the R-Core transformer since those have weird and high amounts of RF.
One could spend hundreds on racks and spikes and brackets or you could spend it on a nice piece of equipment. I'm willing to lay down cash money to say that putting the money into equipment will mean more of a boost in audio quality :) Although, I must admit, I bought some rubber feet for my speakers, but that's because I didn't want to scratch the beautiful walnut on the bottom.
Not the most desirable placing of equipment but a very well use of space I must say. Hahah.
Maybe you can move all the components to the floor while leaving the speakers on the desk to see if there is any noticeable improvement. If not, you can at least be rest assured. =)
I am not willing to spend a few hundreds on racks and spikes. That is just silly, unless, all my equipments cost over hundreds of thousands and I have no better way to spend my money in life.