I ran an iwasaki 6500 on my frag tank, I found some corals did well and some bleached out.
Growth was very good, especially on the monti digis which seemed to love the high light, a frag would honestly grow 1cm a week.
Alot of folks used to run 6500's a good few years ago but then the BLV's and xm10K's came along and to be honest there isnt that much difference in output, I also think 10K is more like what the corals receive in the wild about 10 meters down.
on my main tank I had good growth using a 50/50 mix of 6500 and 20K t5's but the colour was ugly and I had to change
xm10k's are my favourite for sps growth and colour.