I currently have two 1000w Hamilton 14Kk's. Quoting myself from another post:
Advantages of the 1000w lights:
<ul>
<li>More PAR than you can imagine... I could get ~1200 PAR at the corals (9" in the water) with 10kK lights (IIRC), and around 5-700 PAR at the corals with 14kK lights. At the bottom of the 26" tank, I'd get 250-300 PAR</li>
<li>Simpler lighting configuration. Some people may not see this as an advantage, but I've come to the conclusion that simpler is better, and the fewer lights and light types I have to have, the better. I'd rather have two large lights rather than 4 MH's + VHO. That's less bulbs to keep around, fewer types of bulbs, etc.</li>
<li>And who am I kidding, 1000w lights give bragging rights.
Nothing quite says "I'm serious" in the same way...
</li>
</ul>Disadvantages:
<ul>
<li>While the up-front cost is about the same as any other lighting system (around $250-300/light, although the bulbs are ~$120 each), each light is like running a small microwave. All day long... 2000watts or 18 amps takes up an entire circuit. My electric bill from the lights alone (at only 9hrs/day) is $50/mo.</li>
<li>They're freakin hot. People who have normal 250-400w lights and think they know just haven't experienced the full power of the 1000w-ers. I mean HOT - enough that my PVC within the hood had to be covered in aluminum foil b/c it was distorting and melting... and it was a foot away.</li>
<li>That heat goes somewhere, and I had to add active ventilation for the room, multiple fans everywhere, and a chiller. While this is all normal, a chiller runs almost all day in the summer. Add in another 9 amps for 9 hrs/day (we're up to $75/month in electricity for lights and chiller alone).</li>
<li>The latest research shows that there's a limit to how much corals can absorb, so it can be argued that there's no need for much over ~300 PAR.</li>
<li>My soft corals never did well, and I never had coraline algae due to the intense light</li>
</ul>I'd like to make the move to four 400w Reeflux 12k bulbs in LB mini reflectors + PFO or Coralvue ballasts, but that's a lot of money to pony up to swap out lights that are currently working fine...