I use the F32T8/ADV850, and I overdrive the lamps. If you want add some 6500K to mix the color you do so at a rather big efficiency penanty.
Here's a quote from the Ivo Busko article found in the AquaBotanic Informational Library about lamps comparison.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>High performance fluorescent tubes are capable of generating the same, or even slightly more, light output per Watt than MH bulbs. In particular the Philips ADV850 operated under standard conditions even outperforms most MHs. Considering that these inexpensive T8 bulbs can be overdriven by electronic ballasts with high ballast factors (> 1), thus delivering even more light, they are possibly the best option to light a planted aquarium in terms of performance/cost factor. <HR></BLOCKQUOTE>
And about the 950's (6500K) lamps
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>the very high CRI fluorescent TL950, about 30% less efficient (in PAR units) than the average fluorescent. Note that its lumen/Watt efficiency is not that bad though, even outperforming in this respect some of the older high-CRI bulbs. This bulb is a tri-phosphor that seems to use special phosphors that emit light at different wavelengths than the "normal" tri-phosphors found in other bulbs. The overall emission is packed tightly around the 550 nm region, with minimal emission at the blue and red ends of the spectrum. Probably these phosphors were specifically tailored to achieve the extremely high CRI, at the expense of other performance factors. High CRI ratings are usually associated with low efficiency<HR></BLOCKQUOTE>
Here's the link to the complete text. Ivo Busko's Lighting Article