Nuclear Explosion Help? (WIP Animation Project)

I’m having some trouble getting the explosion to look like a nuclear explosion which I need to complete for my first major project I followed Andrew’s tutorial on Blenderguru which is awesome but I didn’t quite get the results I’m looking for so i’m trying again I’m having trouble with the smoke to actually look “mushroom” like and especially the ring around it and the smoke/dust that sets up on the ground in the video which I will post also on top of the nuclear explosion cloud I am trying to achieve that sonic cloud effect if that’s what it is… I’m sure you will recognise it from the pics… anyway I’m trying to do this on a crappy computer which plays the animation at 0 point nothing fps which makes it even more difficult… Please explain to me how to get that ring effect around the explosion should it be with halos or not etc? I may be confusing but hopefully you understand thanks.

Video: http://www.youtube.com/watch?v=hfEMnx-Nz-w

My Nuke:http://i287.photobucket.com/albums/ll156/Dagon14/Nuke2.jpg
http://i287.photobucket.com/albums/ll156/Dagon14/Nuke1.jpg

The effect I want:
http://i287.photobucket.com/albums/ll156/Dagon14/Nuke3.jpg

This nuclear explosion is meant to be placed in a large city I have modeled already as I am working on a project called Project Apocalypse, I’ll post the whole “story board” of the project either today or tomorrow anyway thanks for the help.