Fishy,
pay attention over the next 2 weeks at micro algea growth vs. coralline growth. If micro is increasing change the phos resin and add carbon. A new halide upgrade can affect the balance and take advantage of low nutrients the other lights were not utilizing.
Also, your new bulb should begin to color up your corals over the next 2 weeks also. Your mag, and calcium may also be affected by a growth spurt so just monitor everything closely.
Otherwise the tank is going to really look good in the coming weeks as everything adjusts to the new light. When I upgraded to the 400w lamps on the prop tubs things colored up amazingly fast! The same thing happened on my 250w MH's when I went to 12k lamps. I will be changing my lamps again in May cause my 12k's were about 4 months old and now they are about 7 months old. Make sure you leave a note to yourself on what day you installed the bulb so you know when to change it back out.
HTH, Rich