Don't know if this will help or not, but since I am starting with kessil and looking to supplement with either halide or t5 (looking for same endpoint as you but from the other side). The kessils grow coral well enough but the issue I have with them is that reds in SPS and some LPS (acans in particular) seem to fade to more of an orange and pinks tend to become dull. What is great about them is you do get a metal halide like shimmer and when tuned in to the right color greens, golds, and oranges will pop (and before changing colors, pinks and reds) will pop as much as any other fixture.
My plan is likely to be adding two 175 watt halides (16" shallow reef) to supplement my 2 kessils (4' tank) because even though all my corals have good growth I have just not been happy with the color. If I do this I plan to turn my kessils to almost straight blue and use a 14k halide bulb.
My other thought is to add t5 (my canopy I'm having built will be wall mounted, suspended and only 42" long, tank is rimless so I'm not as thrilled about t5) probably 8 bulbs using retrofit. This way I could stagger the t5's around the kessils and have full color control (having wide color control from both fixtures would be nice) and would still get the shimmer (kessil shimmer is really hard to match).
3 Kessil a360W with your two 250 watt halides would be a good start on a 6' tank (I'm assuming the 150 and 125 would both be 6'). It would not be difficult to add another halide fixture later on if needed. 3 Kessils with the controller will run you 1300. However, if you go t5 instead of led by the time you purchase fixtures and 2 sets of bulbs at one year in you are likely at the same cost.
Just my 2 cents