Hmm, the nutritional info you linked to is for Planet Smoothie, not Smoothie King. I didn't see a Chocolate Elvis on the Smoothie King web site but Planet Smoothie's web site lists one. If that's the place you mean, their web site's nutritional info says it has 630 calories (I'd trust the company's info over that of a third party site

).
Personally, 630 calories would put it in the "never, ever, ever" category for me but if you're a calorie counter, you might be able to figure out a way to have one occasionally.
If you google Chocolate Elvis recipes, there seem to be a bunch of clones out there. I'll bet with a little tweaking, you could come up with one that's a lot healthier and lower in calories.
Got to say, it sounds delicious!

If you come up with a clone, be sure to post it.