you can go to rapidled.com (they have lots of good leds from cree to osram)
most people will tell you to go with cree leds as they are really powerfull
there are advantages and disadvantages to going led, the advantage is that they consume a lot less electricity and produce little to no heat
the disadvantage is that you will be looking at spending a lot of money on them
for comparison a 48 inch fixture from marineland(the reefbrite) is abour 500 dollars
they are not the best in the market but they will do real good for an average user
if you have a little more to spend you can check out the radions by ecotech. for about 900 dollars its not really a bargain but they offer a lot more options than what you would get from other companies
i cannot really point you to a site which would show you par/lux at certain depths but check out this page
http://www.marineland.com/sites/mari...l.aspx?id=4632
and go to the tab specs and size there you will find a par/lux at certain depths
its not that good of a link but its something to get you started with
also check out youtube for a lot of diy builds of led they link a lot of sites that can provide you parts as well
led is still new but it is catching on
i have had my marineland reefbrites for about a year now and they are actually really good but i would advise you to not buy them right now as they are comming out with a new model that has a timer on it
just keep one more thing in mind is that you will need to make sure (if you go diy)
get a good knowledge of the lenses you will need
i am sure there are a lot of people here who can point you in the right direction (i am not that good with diy right now)
hope this helps