xfrog
http://xfrog.com/ does not appear to have a 3DS Max plug, but I would encourage you to grab their samples (there are tons) and play around instancing those in your scene, for starters... It usually only takes a couple minutes each to convert to work well in Octane.
I have not tried any of their plugs or standalone app. I have used their models. Not too shabby. And everything there is 50% off until end of December.