The motion of the emitters is really good in those, so if you replace the particle shape used in the smoke emitters with something that has more detail in it, you'll probably get an explosion closer to what you want.
A few things I did to adjust the 01b nuke:
Duplicated the Smoke Plumes particle type in the left and right free emitters. I then loaded up the August 2006 library, and used the waterflow_new6 shape on those new smokes. That added a bit more detail to the smoke.
I also reset the Tint Strength graph to give the explosion more intense colours.