I'd be careful with this. Turning down a promotion can be career suicide at a company. Can you talk to management and explain your aspirations for the other position?
My brother worked for a tech company called Varian. He took a promotion that didn't pay much more but turned out to be a hell of a lot more work. After six months or so he decided it wasn't worth it and stepped down back to his old position.
They hired a woman to fill the spot. She turned out to be lazy and she knew my brother knew she was cutting corners and not doing the job properly because he had the position before. She orchestrated an effort to get my brother fired which she succeeded in doing because they needed it to work with her and they weren't happy with my brother.
Unrelated to your dilemma, but I can't pass up on the opportunity to tell the rest of the story. That chick ended up leaving Varian then a year or two later she was arrested (and convicted) for embezzling from her new employer. In the investigation it was learned she also embezzled hundreds of thousands of dollars from Varian.
I've got to go now but I'll try to come back later and post the article if i can find it. You know, I can't pass up on the opportunity to spread the bitches name.