I am not sure how much help I will be as I am at a standstill myself trying to figure out where to go next as far as math is concerned. The following link may help and attached to Domanmom's post she has link that was helpful when I was first starting out. She goes beyond multiple step equations, but it has been a while since I did doman so I am not sure if she has added new material or not.
http://forum.brillkids.com/teaching-your-child-math/maths-equations/Have you done sequencing, fractions, or other topics doman talks about venturing into after the multiple step equations, or is this what you are looking for?
Also take a look at LM if you haven't already, the new semester 2 download goes beyond 3-4 step equations.....hope this helps:)
http://forum.brillkids.com/announcements/little-math-1-6-and-semester-2-are-now-available!/