I'm slowly converting over from three 250w Radiums w/Lumatek ballasts to three Kessils and a 4 bulb ATI sunpower - to be done before the summer heat. I replaced one MH so far with a Kessil a360we on a 300g (72x32x30). It's placed in the middle and looks good flanked by the MH. It's definitely not as bright as the MH though, even at 100%. I love the shimmer effect I get from the Kessil and that I can control both blue/white spectrum and intensity with my apex. You can do the same with the Radions I believe with their internal programming. With the Kessil, I have enough customization to get the light the way I like it. It matches the radiums pretty well in spectrum where I have it dialed in. My friend has 3 radion xr30Pro's. And while the customization by color is pretty wild, I don't like the spot lighting he gets on his sand and rocks - I can see individual color bulbs. I don't get that with the Kessils. I also can't do lightening storms if that's important to you, nor integrate with vortechs. But for a tunze guy with an apex, it's the right answer for me so far. Haven't had it long enough to speak to growth.