I know what you mean. Its hard to just 'jump in' to all T5s after having halides, and having such good results with them compared to the PC/VHO's that you might have seen or used before them. Kinda makes you wary about trusting phosphor based lighting again...
Ready for a story...??? I am in the process of buying all of the equipment for my new 130-150g. Its a 42"x36" (almost square) base that will be about 20-24" tall. I already have one of the 250wattDEs I intended to use on it, and I had intended to use another 250wattDE. The tank's dimensions were intended to give me the most possible square footage with only 2 250watt halides for light after all... that was the whole idea. But my success with the 6x39wattT5 tank (I usually only run 4 of the bulbs out of the 6 anyways for a 40B, and I run bluer bulbs at that 2xaquablue, 2x blue+, 2x actinic03) makes me want to use T5s on the new one.. at least partly. One of the best looking tanks (best coral growth I have seen and best coral coloration) I know of is a 120g with dual 250wattDE Ushio 10,000Ks and 4x54wattT5s (2x blue+ and 2x actinic03). You know how some T5 lit tanks have a very pastel, yet slightly faded coloring to the SPS? And you know how halides give many corals a deep intense coloration? Ok, combine those two together. His tank, with a 2:1 halide-T5 wattage ratio has some of the most intense coloration for any of his corals that I have yet to match with any MH or T5 only system.
So then I thought, why not run the one 250wattDE I have with 6x39wattT5s on the sides of that? Ok, sounds good, but If Im going to get the same great coloration, and then considering what bulbs I would use... (with the dual halides I would have just used two pheonix bulbs)the MH+T5s that I would most likely use would be a 10,000K for the 250wattDE and 4x blue+ & 2x actinic03 for the T5s. But that would give me a really bright 10,000K spot in the center of the tank, and less intensity all around the rest. So the best I can come up with is using a slightly bluer bulb in the 250wattDE, like a pheonix or ushio 14,000K, and then using my existing T5s in a full spectrum arrangement of 2x sun, 2x blue+, 2x actinic03... But that would mean less overall output for the halide, or a 'hot spot' in the middle of the large yet shallow tank... so then why dont I just do all T5s then?!?!?! Lol.
I know what you mean, to say the least. But recently I saw a friends tank who I had helped with new lighting suggestions. He has a 150g, with 2x250wattSE 20,000Ks at each end, 1x400wattSE Radium in the middle, and 2x 160watt VHO's. His tank was very blue to say the least (every coral in the tank was either blue or green even if they really werent), and sucked up wattage. He also had a 40B with a big halide over it for his frag tank...just like I have. I suggested he try T5s after I saw how much brighter my 6x39wattT5s were compared to my halides... so he bought a 4 bulb Tek with 2x sun bulbs and 2x blue+ bulbs. He loves it. Because of the sun bulbs, he gets that intense coloration (not faded pastel) look in his SPS like halides do... there are many corals in this tank that look better than under the halides. I saw it, and was very surprised how nice the combo really is. The sun bulbs look red/green and pukey when I tried them (but I tried them alone and decided against them), but with the blue+ bulbs to even them out... they look awesome... much like a ushio 14,000K. His corals looked awesome too with that light... the tank looked much brighter, and the overall wattage for that tank went down by 100 watts. Then he swapped out his 150s lights for a combo of halides and T5s (a 72" maristar... he was confident in T5s and DE's, but reluctant to make a 100% change).... reducing his overall wattage, and getting a much brighter tank (using 3x250watt Ushio 14,000Ks and 4x39watt Blue+ T5s)... so much that a couple deepwater acros bleached out. The combo has also colored up his corals to the point where I can say the previous lights werent doing his tank justice... he actually has corals that look really sweet that looked ordinary before. Now, he is considering just removing the MH/T5 combo over the tank and going with all T5s (when ATI gets the 5' powermodules here)... 6x80wattT5s for his 150g... and he is wary that it might be too bright for some of the corals towards the bottom of the tank, because he sees now how T5s really do penetrate so much better than his halides.
I know you might be reluctant (I am too), but a T5 only tank would be the smarter and easier thing to do in the long run. You just have to keep telling yourself that until you get it set up and you realize it. There is just no reason for the halide other than 'its what you are used to seeing'. One trip to Germany to visit the shops there, and you wont even doubt T5s or wonder any more.
The only other option I would say is to save up for a LED system. As much as T5s are the present best technology, LED's promise to be the next big thing... dont know if they are quite ready yet though... but its not going to be long before they are for sure. Maybe in a couple years we will see a Maristar with LED's for main lights, and T5s for supplimental...