Changing lights

I would go with your second choice & change them all at once.

ATI & UVL are much superior quality bulbs then coralife.

 

check this out http://reefcentral.com/forums/showthread.php?t=1706461&page=21 also this is grims page http://tfivetesting.googlepages.com/ grim suggests 4 Bulb Suggestion

Blue Plus, Super Actinic, Aquasun, Blue Plus

 

I have a 4' Giesemann Aquaflora bulb I'm no longer using. I wanted more blue in my tank so I traded it out for an ATI Blue+. It's only been used about a week. I'm not asking any thing for it, but donations/trades are appreciated. I'm in Cedar Falls if you or anyone else is interested.

I am running:
2- ATI Blue+
1- ATI Aqua Blue
1- Giesemann Actinic Plus
along with a 4' and 3' actinic VHO's and I think it looks perfect. I just got my ballast back from Ice Cap for a repair a couple weeks ago and I can already see new growth on some sps and the colors of the corals are amazing.

 

Karen,
I would dig around in the forum amasia metioned as well as searching for some pics of different lighting scenarios to help you decide.  I was all about ordering the KZ Figi Purple until I read in several places that it's overpowering in less than a 6 bulb configuration and all of the pics I found with that bulb in 4 or 5 bulb configs looked too pink for me.
I have a thread on Reef Central asking a similar question and the resounding answer was the UVL 75.25 & Blue Plus.
I ended up with a 75.25 & ATI Blue Plus to supplement two of my stock bulbs in a 216w unit...still deciding on the other 2 bulbs.
I've never heard of anyone spacing the replacement of the bulbs...to get any real benefit for the corals it wuld need to be over serveral weeks not days.  If your corals are adjusted to the intensity of T5's there shouldn't be issues.
How old are your current lights and are they 36" or 48"?
-E

 

http://tfivetesting.googlepages.com/

Here is some more grim reefer reading.