Discovery Plus 4 vs. Discovery Essence

As an IC between CD and Pre, is the Essence worth the upgrade from the Plus 4?
There is not a major difference between the products. The Essence is slightly more extended at the frequency extremes and somewhat smoother overall. No real need to upgrade, but if you do, you won't be disappointed. I believe Discovery sell factory direct and offers a trade-in policy.
I am currently using Discovery Essence between my CD and Pre. I totally agree with Onhwy61's response.
Onhwy61 and Timo - thanks for your responses. I have one "dumb" question. Exactly what do you mean by "smoother"? (I seem to like a bit of "edge" or "grit".)
It has less of a sonic signature than the +4.