What's wrong with the way it is using halogen type bulbs?

If it works, don't fix it.

I don't understand the need to use LEDs, especially white LEDs. Personally, I have built 5 LED light sources for use with 8x10. They are a pain to get them right. Diffusion without attenuation is the worst of it. And cooling. And drift. I only made mine because I've been designing LED drivers for customers (for projection and simulation) for years and decided to make one of my own. They all work fine now, but it has been a long road with many problems. I made a few for friends, but no more. Takes too much time and money.