I wouldn't say 5500k is VERY white, but IMO isn't VERY yellow either. I've used both a Venture and a Hamilton bulb. The 5500k color temp is what the sun is supposed to look like at noon. It is very bright, but does benefit from a little actinic supplementation. The bulb grows corals very well.
I'm running a Hamilton 5500K right now from a used fixture I bought on ebay. I seems to be a bit yellow/greenish. My xenia is doing great under it, but its not very pleasing to look at. I have a 10000K on order.
The 5500ºK bulb is much whiter than the 6500ºK Iwasaki. If used alone the tank will only be slightly yellow. With even 28W actinics it will be just fine.
FYI - The Venture 5000ºK and the Hamilton 5500ºK are the same bulb. Made by Venture and relabeled by Hamilton.
The higher the K, generally indicates the bluer the visible color. The 6500K I am using right now is definetly yellower than 20000K I had before. Next time to replace the bulb, I will switch back to 15000K