Say Bugs713. I've been checking into possibly doing a DIY LED lighting system before I have to replace the T12 vho bulbs I have. I've been checking through the DIY forum here and found this pretty incredible thread. The link is to page 13. Check out post #317. I'm only on page 15 or so of about 25 pages. This thread has two guys in Sweden experimenting with LED. Very detailed and excellent stuff. Post #317 shows a test one of the guys, Lassef, did in a 14 foot deep tank.
http://reefcentral.com/forums/showthread.php?t=2128756&page=13
I went to Fry's ellectronics yesterday to see if they had any of the components listed in these LED builds. Not really much at Fry's at all. These guys are going through eBay. The links to specific parts are included throughout the thread but you do have to take notes or bookmark (I do anyway or I cann't locate it later...). Plus there's videos of how to do it, as well.
Bottom line, to answer your question about will LED go deep enough. It looks like LEDs have surpassed MH in penetrating.
Another neat thing is they are using multichips instead of individual LEDs. So they are compact and easier to build. They wattage ranges are pretty wide, too. From 10 on up to 252 watts. Kessel's new A350 doesn't put out that much.
Got pretty excited when I started reading that thread. Guess it may show here. Sorry if I hijacked your thread.
BTW - been following your thread and I sure like the way you did your rock build.
Cheers!