it will work.... most easily purchased MH bulbs are in the 4500K range... so sometimes you have to do what you have to do.... save the cash
it depends on what you are gonna use it for the easiest way to remeber the K scale is to think of the numbers as colors.
So get dont get... I bought a 2 pack of 28watt 5000k for 5 bucks, too good to pass up That was actually a really good deal because its like getting a 56 watt for 5 bucks and my 42s were 10 bucks