Thanks Milad. I will look into the Inventronics as well.
It looks as though 4 LEDS with 40 degree lenses, one shining into each corner, will have enough overlap that I won't need a 5th LED pointing straight down (although I might anyways... I'm really afraid of having TOO much light and starting an algae farm. Thus my want/need of a dimmable driver).
With only 4 LEDS, there don't seem to be any power supplies capable of pushing the 1-1.5A max current at such low voltages. For instance, the Inventronics 1100mA 50W LED driver bottoms out at 16V. With 4 XP-G LEDS @ 1100mA, they would drop roughly 3.3-3.4V which would only need ~13V potential... Thus it seems I am stuck using the 700mA driver, and powering the LEDS at only half capacity.
Am I looking at this wrong?