Got the E12a back from my boss after having lent it out to him for a week to try along with the KZ7 I encouraged him to order. He's the type of guy who wouldn't consider himself an audiophile in the least, but he does enjoy things that give him more excitement out of the music he listens to. Here's his very un-seasoned impression of running the KZ7 over the weekend in concert with the E12a:
He wasn't sure the amplifier would do anything to the overall sound at first, but was immediately blown away at how much more spacious the tracks he'd listen to seemed to get. The punches got even punchier (his words, not mine)! He also put on a relaxation app he usually listens to on the weekend for meditation because he wanted to see if he could pick up on some of the microdetails (my choice of words this time). What surprised him most was that he could hear one sound close to him and, on the same plane, more sounds behind it. Gave me the perfect opportunity to explain soundstage and imaging to him.
He also tried the E12a on some of his other earbuds and didn't hear much of a difference between amped and not-amped, but kept gushing over how there was a marked improvement over the ZS7 being amped vs un-amped. After begrudgingly returning the E12a to me, he's all smiles. I suppose that's one very enthusiastic pair of thumbs up
Now that I've got the E12a back in my possession, I'll spend the week using it along with my pair of ZS7 (on stock medium tips) and the A45 for DAP duties to see what my overall impressions are. Once the Opus#1 shows up, however, all bets are off.