Oh well. When GPU mining hits, I just hope there's comparable performance between Nvidia & AMD (I only got a couple of the cuda variety). Better yet, have the advantage over at the cuda camp, that would be very nice! 
Good news for you then. We are still tuning things (and we're sure the community will improve upon it once we release source), but at the moment our Nvidia numbers for high end cards are better than our AMD numbers (thank djm for that).
Since zr5 is a variation of x11 with 5 algos, AMD must be way better.
I wonder who is helping you with implementation of AMD GPU miners.
If you want someone to do it right, Wolf0 should be on your team testing miner for AMD GPU's.