The epsilons bass is more accurate tighter and rmore controlled plus you can adjust The output of the bass with the SCU box, the kappa 9's bass is good but a little thumpier sounding to me.
The k9 has more air on top in the highest frequencies due to the SEMIT, wish the epsilon had one, the epsilon tweeter goes lower and sounds like everything has more body to it.
The midrange goes to the epsilon, hard to beat an EMIM
The mid bass is personal preference, the epsilons mid bass is faster/accurate but the k9' mid bass hits harder, take your pick.
The epsilon has way less coloration coming from the drivers and cabinet.
The epsilon is way more revealing of poor electronics and recordings than the k9, in fact because of that I find myself listening to the k9' half the time because they are a more forgiving speaker.
You really can't listen to rock and such on the epsilon, it sounds bad, but pretty good on the k9's, I can listen to more genres of music on the k9, the k9 is a little more dynamic in the mid bass and mids.
That said give the epsilons well recorded recordings and you are in for a treat, I like to listen to soft rock, 70's early 80's music and live acoustic and solo's on the epsilons.
I like both the epsilon and the k9, just for different reasons, both are good speakers.