Just be sure you adjust the height accordingly. I put a 150W DE Phoenix 14K over my 10g shallow vat. I tested it with a couple of SPS frags, and burned them all. 12" was too close. 20K will be a bit more forgiving, though.
Very cool, I am extremely tempted, will I see a huge difference as compared to my 96watt 50/50 PC? It's practically new, I'm a sucker for reef tech (lights, skimmers, etc)