If you are going to use Cree xp-e or -g lights you will be fine. Spend the money on good drivers and Heat sinks, ensure there is proper air movement abd you will get long life and the most efficient.
I am running AI sols on a 100 gal 60x18x24...more than enough light at the substrate for even a heavily planted tank even at 40 percent for 8 hours like I am running. Granted they are 72 watt 30 led fixtures, but you can broswe reef central for some par readings..Some guys are getting 200 at the substrate under 24 inches of water with fixtures hung at 12"...
Things to remember...even without optics, a "flood" setup, they still are rather spotlight-ish...optics will help to give a more uniform spread and allow you to keep most of the light in the tank. The good cree units will provide plenty of light, sp you can use the height over the water to adjust the light coverage.
Also I don't think 24 LEDs will give you very good coverage, it will light the tank just not evenly. That's the biggest drawback to led tech is you may have more than enough wattage, and possibly coverage, but it gets uneven and appears spotty easily. There ar some charts on some of the sw forums showing how coverage works. I would do two rows of 16, 10 or 12 each row white, the rest blue. 12 and 12 will be very blue. My tank is 18" deep and I just have the one row of fixtures and with optics I get perfect coverage front to back. But each fixture is two rows of pucks.
I also highly recommend dimmable drivers. Led with that sort of setup provides a lot more light than you realize and can grow algae quick and your fish may not like it. Also remember the color rendition as it appears in photos will be different, very different to your eye. A lot of guys change their color settings to suit the camera for pictures then switch back after because of that. So don't "judge a book by it's cover" as it's often hard to see on camera.
If you can try to see a setup in person at a saltwater store just so you can get idea. Also peruse the hundreds of DIY threads on reefcentral for lots of help and good tips and pictures.
My ai sol build thread is in the equipment and supplies section--"bringing high tech led lighting to the freshwater world"...sorry I don't have any links a lotta work to do on an iPhone