I did quite a bit of research into T5 lighting before I switched over from my old metal halide setup. Like you, I also was planning on going with all ATI bulbs despite how hard they were to come by at the time. Then I stumbled across this article:
http://translate.google.ca/translate...F_enCA273CA273
Seeing as aquascience bulbs are carried by most of our Canadian vendors, I thought I'd give them a try based on the results of the above experiement. So far I'm very happy with the 22K and 15K bulbs however I haven't tried any of the 17.5K duos yet. The 15K bulbs are more like a 10K bulb though as they emit a much more yellow colour than my Kz 14K New gen bulbs.