Or was it simply expectation bias?
Did you A/B one dac/speaker setup vs the other? I can see better speaker positioning possible with removing them from the desk altogether, tho, that's not a great place for speakers in the first place. In the spare bedroom where my 305s are I'm sure better placement would do more than raising them off the surface of the dresser in any case. It just irks me to spend money on Auralex foam, can do just as well with household materials at hand.