I have never heard an Evo Aeon or an Innuos Zenith so I won't pretend to know how they sound. However, I bought an Innuos Zen when I was looking for servers under $3k and wanting a unit that sounded clear but smooth and non-digital. My dealer recommended the Zen as the "sweet spot" in the Innuos line and as sounding fuller and less edgy than the Lumin servers they also carried. I later added the Phoenix USB reclocker to optimize the USB signal path, and the new Innuos Sense software has taken my system to an even higher level.
Just to further reinforce the reason for an in-home demo, I have noticed that it's common for Agon members to throw out a quick comment about sound comparisons (e.g., "Gear A destroys Gear B") without always specifying how the gear differs in sound. For me, I look for sound that is smooth, full, dynamic, and natural while providing enough transparency and detail to sound "real" but not so much that it sounds "bright" or "edgy." In contrast, I know listeners who want maximum detail because that's what they like and that's what their system thrives on.
So be sure to buy gear that you like - not just the gear that someone on Agon likes.