use the goldwell color remove. then use either 1/2 6n 1/2 6GB or 1/2 6n 1/2 5bg, the N will neutralize any red that didn't come out with the color remove. you could also use the color remove and the demi color line. With goldwell don't be afraid of getting to ashy, as long as its not bleach blonde and you want it dark... if so fill it.  

yeah I would suggest the color remove as well and see how much of the red that you can get out.  I find the NA's to be really nice as well and if you have a lot of red in the hair don't be afraid to go in with the A's either.