Very deep tank, might get hard to light up the bottom but might be good for softies and mushrooms on the bottom and the light needy corals on top of the LR structure, But on the other hand you might have trouble getting your hand down to the bottom if and when you need
if you make your overflow box bigger, say like 13x20 you can also fit your return threw the tank's bottom and you might even have room for a Durso stand pipe
You don't think your limiting your self in the LR structure by having the tank 50cm vs 60+cm ?
I have a 66cm high fresh water and i hate having the reach for some thing that's on the bottom since my hand reach is 63cm so i personally don't like to go higher then 60 - 70cm high
Cool tank, go for it, would think 3 250w mh and 4-6 t5 would survice this tank fine cause there is such vast variety of liveforms to choose from and many of them don´t requier all that much light to thrive. I have a 400 l juwel with 3 250w mh 20000 k and 2 t8 blue and 2 t5 sun glo works damn fine!.