Interesting. I've wondered how a Snom would work. Be sure to update us with how you like it.
If it works like the other phones I've worked with, 1st thing is to be sure you program more than one line in the 3300 for the phone. I'd program them as Multicall lines for simplicity if you can.
After that, I would have to think you'd browse to the Snom and program a second line on it.
Ralph