Sometimes when I change DAC, speakers, soundcards, etc I feel the later its better,
but I would advice to give some time to both cards and then consider again,
as for the Elite, don't forget its price tag when first released, its totally different with the other xfi cards, and I think its still the flagship of Creative,
so, no surprise if its better then the essence..
As mentioned most creative cards are good with soundstaging. I can´t recall if the Elite Pro improved in that matter over previous X-fi I would think they are quite similar. But the lower noise floor and no hiss certainly helped over my previous Creative cards. The Elite Pro was simple a lot cleaner, better dynamics, smoother, richer sounding.
As for Elite Pro to Essence ST it´s just as clean. Dynamics is the same but the Essence. It´s smooth it´s mostly the soundstaging and the balance it fails a bit at for me. And the driver department it´s not even trying to compete in. If you put the cards side by side the Essence ST impress more with their bigger sizes caps and such. But that is partly due to it´s amp section.
The stock opamps I found was rolled off in the highs on the Essence ST. It was great for the K701 which have a bit of hot treble. They also have a nice bass boost which suited the K701 but none of my other gear needed that. I haven´t experienced much ear fatigue on it or the Elite Pro for that matter but I rarely listen to above 80 db anyway. Not after switching to the 49720s either.
As for new toy syndrome I know the Elite Pro inside and out so it´s not really new. I suppose my ears are burned in on it lol. I have for some months exclusively tried to get into the Essence ST but also my Keces DAC 131.1 mk 2... It also trounches the Essence ST particularly in term of soundstaging as well. I value soundstage a lot I have figured out and I don´t need much extra warmth. Proper soundstaking just make the instruments sound more real and let you buy the illusion of live sound more easilly.