WHen I built moonlights for my reef tank, I used Cree 3 watt LEDs. I bought them off that famous site where you bid on stuff. They ship from Hong Kong, but they don't take long to get there and cost something on the order of $15 for a 5 pack if I remember correctly.
I don't know how many you'd need...
I know the Solaris system uses an MCU controller, more than likely with a PWM based control gear to dim the LEDs. They use at least two different colors of LEDS, varying the intensity of each color to achieve different color temperatures.
Those Cree LEDs tend to heat up, and failing to keep them cool can really shorten their life. I run mine off 12v switched with TIP31 darlington power transistors, so I can control them directly with TTL outputs from a microcontroller. I can't remember which resistor I used, but I think it was something like a 220 ohm 5w power resistor on each. I bolted each LED to a small piece of aluminum angle material with some thermal compound and that addresses the heat issues.
I have no idea how advanced in electronics you are, but I bet some programming with a PIC MCU, a serial LCD, and a RTC IC could yield you something similar to the solaris.
I would think your biggest challenges are the lenses, focusing the light in the right direction, and finding LEDs for a decent price that will match the proper color temperature. Solaris certainly isn't going to share what the wavelengths of their LEDs are.
