I have a pair of 290x. With Crossfire enabled the frame rates are terrible and there is extreme stutter.

Now I know one card is enough for Skyrim and really it is. But with some of the more aggressive ENB's with Ambient Occlusion enabled your frames will drop. From what Ive read ENB and Crossfire do not play nicely and even Skyrim itself and Crossfire do not get along. But then I read about people who have no problems running Crossfire so I am left not knowing what to think.

So having said that, is there a trick to getting Crossfire to work?

You just have to be lucky really. Dual GPU setups are a cobbled together technology that does not really work. Has to do with all the issues parsing the data between two chipsets and keeping that all in sync. For most people, in most games, Dual GPU's offer no benefit over a good single card. Skyrim as a game does not benefit from dual gpu's for most anyone who uses it. Best you can hope for is there is no drop in performance on this game.

Dual GPU's do make the video card manufacturers more money, so there is some benefit to some people, in that regard.

ENB is post processing that can cause huge framerate drops depending on the effects used and your system. There are issues with some crossfire setups.

Not sure what CPU you have but with ENB and crossfire your CPU load can go up significantly. Your CPU now has to feed 2 GPUs as well as run the post processing on each frame before it sends it off.

What CPU loads are you getting? if your CPU is running 100% xfire enabled + ENB then thats a possibility. The amount of memory used can go up as well. Im betting you have enough RAM.