Does anyone know what is the internet speed that the 4305 or 4350 can support?
Also, is there a module that will allow this box to have 8 port POE like the 3448?
As there is no 4350, I'll assume you only mean the 4305.
There is no module you can add to the 4305 that could give you an integrated 8-port switch.
As for how much bandwidth the 4305 (and others) can deal with, the performance numbers on these units is listed in the AOS Feature Matrix and can be found here: AOS Feature Matrix - Product Feature Matrix
Adtran Applications Engineering