Play around with the calculator in this thread: http://www.plantedtank.net/forums/di...-tank-led.html
I would use a 3.25 inch spacing of the LEDs, one row, about 8 LEDs, Cree XP-G, either all cool white or 5 cool white and 3 neutral white. At 18 inches distance, with 40 degree optics you should get about 60 micromols of PAR, high light, at 700 mAmps current. If you want to use a knob to control the light intensity, use the D version of the Meanwell driver.
A single length of 1" by 2" by 1/8" or even 1/16" aluminum channel should work fine for the heatsink, with no fan. I would put the LEDs in the inside of the channel, to help shield people's eyes from the LED glare.
I haven't used the solderless connectors, so I don't know how well they work, but if you are uncomfortable with soldering, I feel pretty sure you would be satisfied by the results with the solderless kit.