Horace, Horkn and I have a mutual friend, Bill, who has the dual 250wattDE + 4x54wattT5 setup you mention...it works great...for his 120gallon!!! Putting that over a 75 would be overkill.
Horkn, I was thinking that the halide would be a bluer bulb, as a daylight bulb in the center with the T5s might be overkill, and the shimmer is all JD is really looking for. So a 250watt pheonix or radium, or heck, a 20,000K XM. With how blue JD runs everything, the T5s will be the primary source of his PAR, not the halide.
What 4 bulbs? Well, first, I would run the Icecap 660 ballast...it will overdrive those 80watt bulbs to 100watts, and give a proportional boost to the output w/o shortening the bulb life like many are reporting with the shorter bulbs that get overdriven by 50% or more. Or not...the IC660 is an expenive ballast, and I suppose 80watts x4 isnt bad at all. Heck, it might be too much as is.
As for the 4 bulbs... JD likes his blue, so I would skip the GE 6500K, and use this combo...2 aquablue, one blue plus, one actinic plus. Or, since the actinics are pretty pathetic in output compared to the blue plus, just use 3 blue plus and an aquablue (11,000K daylight is really what it is). Or, yet again, 2 aquablues, and 2 blue plus. That would be the brightest combo while keeping a nice 14,000-20,000K look.
Or, the other option might be to use smaller halides...much smaller halides. I know JD might not like that though with his existing investment in ballasts...but maybe his other half has resources...
If the halide is just for shimmer, and beyond that, just for looks. Perhaps just running three small halides...175s, or better yet, 150wattDE (I have heard of the reasons why JD doesnt want to use DE though...but the 150DE does have a much differrnt socket than the 250s and 400s). I know JD doesnt like 10,000K much either, BUT, it would be for effect, and that yellow light would be minimal compared to the T5s output. When you look at the spectral output of the 10,000Ks, they actually contain more actinic than any other bulb...even 14,000K and 20,000Ks (except for 6500K bulbs which do have more, but hardly anyone uses for show). 10,000Ks have a significant actinic output, its just all the other warmer spectrums that cover it up. So what you do it kinda what Bill did. You get 10,000Ks, and suppliment with blue plus T5s (Bill also uses actinic plus, which is kind of a waste when you think about it) to give them a similar look to 20,000Ks and 14,000Ks (the blue 450nm spike is what makes bulbs like the pheonix and radium look so blue, not the purple). So heres my suggestion using 'spectral addition' of 10,000K halides with T5s.
Use 4 blue plus bulbs, or one aquablue with 3 blue plus T5s, and three smaller halides at 10,000K...175watters (to keep the mogul sockets), or better yet 150s, which could also allow for enough room (due to the smaller bulb) for an extra T5 bulb or two.
Bright as all H#LL. There would be such a huge blue spike that the 10,000K would get covered up, and since blue+ bulbs are perhaps the strongest PAR performer for T5s except for GE 6500Ks...it might even melt his shrooms on the bottom still...lol.
The late Grim Reefer wrote me this in a PM at another forum...
"I did PAR readings 18" under the surface on a reefoptix lll with a Hamilton 10K and on an EVC electronic ballast (250watt). With the fixture raised about 2" above the tank I got PAR around 150. That unit would reay need to be at least 5" above the tank to prevent it from boiling the tank. a 4 lamp Ice Cap T5 system an inch above the tank did 183. I would have raised that another inch or so for permanent mounting so I would guess the PAR would be in the 170 range. The Ice Cap system used 303 watts to produce the light. I would have to run 2 halides to cover the same area the T5 did which would have used 520 watts plus whatever actinics would have been needed. The T5's were 2 aquablues and 2 actinic plus. My 3x250 halide system pulled off 95 at the sand with new EVC 14K DE's. I put some bright 10K's in that were a little too yellow for my taste and they pulled of 120's."
It seems T5 really does give halide a run for the money...beyond the shimmer effect...
But lets see...that would be 150x3=450, + 80x4=240...450 (halide) and 240 (T5) makes 690 watts total, and I believe that would be a similar look/output to what he has now...except for a tad more daylight up at the very top where the halides might overpower the T5s around the bulbs a little. But 690 watts only...not a bad energy reduction.
As for the tek lights, I wouldnt use them on a 150. The icecap SLR reflectors are better for taller tanks (unless you intend on a 20% comparative PAR drop at 18" with the tek to give the lower light corals a chance down below). If you did buy 3' tek lights though, the best place I have found was ebay. I bought my 6x39watt Tek off there for $250. Ebay and horticultural suppliers are the cheapest places I know of really...much less expensive than reefgeek and other reef stores even.