ok, using your setup...
2-4 Smart String Controllers. (SSC)
if you have a relatively short cable run, you can use a 4 port passiv hub with the USB Dongle. (as long as it has the pixelnet firmware)
i wouldn't reccomend a 4 port passive hub with a EtherDongle, as it limits you in what you can use from it.
using an EtherDongle, you'd need to use a 16port Hub (Active or passive)
yes, there are ways to use one, but then you really aren't using the equipment as it was designed.
most flexibility, I'd reccomend using the 16port active hub, so you can always add dmx devices to your setup, and wouldn't have to worry about buying more things later, when you could have done it now.