I did it and I wouldn't recommend diy. Kessil is probably the least expensive and is a great fixture.

Aside from the 10, 20, 30 watt multi chip LEDs, 100 watt and larger have been available for some time. They can also be had with different colours on the same chip. With optics, one or two of these would make a diy project much simpler with respect to number of components & soldering. Great option for deeper tanks I would say. Downside is heat management becomes a bit of an issue & all your eggs are in one/two baskets. You need a massive heat sink with fan & if that fails.... Prices have dropped significantly though, so replacement of a cooked 100 watt chip no longer hurts quite as much. The Kessils are similar, using a 30 watt multi chip I believe.

If I were to do another build, I'd seriously consider the larger mjulti chip LEDs.
Here's just one example of something I found with a quick search.

http://www.leds-global.com/100w-hybr...ium-p-306.html

And for the non-DIY folks, if you have deep pockets, here you go.
http://www.ecoxotic.com/100-watt-ell...annon-led.html

The a150 uses around 30 watts, and the a350/360 around 90 watts. These are custom chips and optics, not sure that comparisons with diy options would be accurate.

That all depends...
http://www.ebay.com/itm/10W-Cool-Pur...05591137?rt=nc

http://www.ebay.com/itm/251706226157...%3AMEBIDX%3AIT

3x 48" Light Frames - $216.00
20x Pure White ( 6000K ) - $ 23.49
20x Warm White ( 3000K ) - $ 23.49
20x Red ( 620-625nm ) - $ 77.07
20x Green ( 520-525nm ) - $ 65.79
20x Royal Blue ( 452-455nm ) - $ 31.01
10x Purple UV ( 400-410nm ) - $ 99.63
1x 48V 480W Power Supply - $ 53.89
20x LDD1000H - $150.00

The only expensive option there is the UV LED's.
Other than that for around $500 I can have 500W+ a full WRGB&UV setup! And this is more of a buy bulk and use what you need, keep rest as spares sorta deal.

Now group the colours by channel, throw in an Arduino Due for control.
With the right programing not only you can simulate a complete solar and lunar cycles but also have a lot more features you can ever need!
Need OR Want tank monitoring ( Salinity / PH / ORP / Temp ) ??
You can always add more:
Wave maker, skimmer control, feeding control, open / closed loop control...
List goes on, and on...

As I have stated earlier...
My setup is a deep 150 so I need a lot of light to keep things happy in a 30"+ of water. Also with me traveling out of town for work sucks and its hard to know exactly whats always going on.

I would say there are some things you can cheap out on if you go DIY but I wouldn't cheap out on the actual LED's. The output per watt really varies.

I have both DIY and one of the dimmable Chinese 120w off ebay. Went and bought the best LED's I could find for the DIY and the light output and quality does not compare. Visually I would say I get twice the light output per watt from the DIY than the ebay fixture, better colour as well.
I cheaped out on fans and power supplies... have had trouble with both...

I checked the both the "eBay" brand VS Cree and other units on the market.
If the datasheets are "accurate", they are in fact on par with the Cree XM-L units. However... The Cree units have a 3A draw VS the eBay brand at 900mA, which means that these units are more efficient than the Cree units.

But then again... It is eBay. Some are good finds and some are just assembly house rejects. I will get a couple of these units and confirm first...

These heat sink/frames are pretty neat. Never heard of having a heat jacket tube designed into a heat sink & using it to feed warmth back to tank. Good link.

It would be neat to throw those side by side. Both showing close to the same lumens @10w.
I deal with LED lighting for general lighting applications through work and they all seem to vary. Rated hours can be from 25k up to 100k, CRI can be from 60 to 90(visually a huge difference, 100 being daylight). The pricey LED fixtures(non marine) score high in these 2 categories.

I would post pics of the differences between the 2 fixtures I have but they would both look like crap with my photography skills.