How much Light for 4 foot tall setup?

[Ocelaris]

I'm making a new orchid tank, and I am trying to figure out how much light for vandas, as that will be my primary plant in this tank. I know 4 foot tall doesn't seem like that tall, but for an indoor tank with a 2 foot cabinet underneath, it's about as tall as is reasonable.

How much light is enough?

I have a plan of 2x 150w Metal halides putting out 12000 lumens each... I already have a 150w Metal halide, and a spare 100w MH, so was thinking I could just get another 150w setup, and reuse the 100w (which puts out ~9000 lumens initially). I'm trying to stay within/under that 500w boundary. maybe 2x150 + 1x100?

How bout it, anybody have any ideas? I want to stick with straight Metal halide, as I need as much penetration as possible... I'm not totally opposed to 2x 250 which put out 18,000 lumens each or roughly or a single 400w which is around 30,000 lumens.

I'll be sure to share when I pick stuff out.

Here's the bulb spec sheet I am looking at:

MHN-TD M81/E 150W/842 RX7s 1CT

it's a 4200k 85 CRI bulb, rated pretty highly by this comparison:

Aqua Botanic-light bulb comparison

Anyone with high lighting requirement plants want to share what quantity of light they have?