Ye the 125w dual spectrum should be ok for one plant, i would prefer the larger 300w myself but thats just me.
With dual spec'd cfls they are more or less 50/50 in blue/red spectrums.
That sized cfl is an E40 fitting you going to need a reflector with that or a E40 bayonet fitting.
If a reflector is required, get one with a dimpled/hammered finsh on the inside as they are much better at spreading light about than the plain polished finsh ones