I have a 48" 6 bulb fixtue running on my SPS dominated reef. I'm currently using -
3 ATI Blue +
1 GE 6500 Daylight
1 ATI Actinic white
1 ATI Aquablue Special (12000K)
Supposedly ATI bulbs put out more PAR than Geissman though G's are very good too. My tank has a bluish look, but not overly so - maybe around 14000K? All the corals are doing well (nice colors and growth though this is obviously just my opinion) - blastos, duncans, acros, zoas, millipora, etc.
There's a relatively new brand on the market - Wavepoint. I haven't heard or seen any long term results, but limited comparisons put their bulbs with the highest PAR. However, it should be noted that PAR alone is not the be-all-end-all of marine lighting.