I would highly recommend Ian Harrop & associates
Not just because we used them but because our case was complicated.
We had divorce, a child coming over and then defacto relationship to deal with (not to mention court) but he sorted it all out and here we are. Mine was done in about 6 months and the defacto in 9 days.
Cant remember the costs exactly but they do a free assessment to find out if its worth pursuing. They also so offered a no win no fee service. That way they wouldnt take you on if they dont think you will pass.
This was almost 4 yrs ago so hopefully nothing has changed with them.
Ian himself worked in the Australian Immigration department and knows what they are looking for. That swayed me to use them in the first place.