Not being much of an expert on Particle Emitters myself...tho I play around a bit and find Particle Illusion SE sufficient for my basic needs,layers would be nice but the work around to that is to render to a lossless codec and then rerender over that.

So have you tried the demo ?

Wondertouch  also has a bunch of tutorials and a forum I might suggest you check them out but anyway for $99 there is quite alot you can do with it.