http://www.dealextreme.com/details.dx/sku.2395 is the LED I plan to use, a Q2 bin, less efficient version of the Cree 3 watt LED. I plan to mount this so it is 17" above the substrate, and I extrapolated the data from the nanoreef thread where the poster actually measured PAR intensity at two depths in the water - heights above the sensor. I'm not yet fully committed to this, but having spent as much as I have I am almost certain to go all the way with it. Any PAR data I can get will be extremely useful.
I won't need any secondary lenses since the distribution is pretty good as it is, at that depth. And, yes, it will be in my existing fixture, which will reflect side light back towards the tank.
This has become an all-consuming obsession for me!