If I read you right you are thinking of replacing 2 65 w pc lights with two 24w lights. The PC lights are by design a little inecficient and the t-5s depend on quality reflectors.
I have some pc lights i still use and jl has bulbs though the shipping cost is the same if you get one or a bunch of bulbs.
http://www.jlaquatics.com/info/202/P...aight+Pin.html
They also have straight pin if that is what you need.
The 2 bulb t5 might keep everything alive but a four bulb might be better in the long run and will give you more choice to tune the color. The 6500k bulb may grow the corals faster but they may stay fairly brown. You might want to put a more blue bulb on instead.