For those of you looking for a 16x16 USB audio interface, combining 2 x USBstreamer will work well. Here are a few tips and tricks depending on your software:

For Mac users(an OS who understands multichannel Audio.. ;-): The trick is simple since it's already embedded inside the OS. You can do so following the steps of creating an aggregate audio device. Here is a very well written step by step:

For Win users: Knowing WDM/ASIO requires a unique ID for each interface, you'll need to use a dedicated firmware for each interface (i.e. flashing a custom unique SN# for each USBStreamer). Look under the Userdownloads section for the firmware. Load one binary to one USBStreamer, another binary of the other USBStreamer. Installing ASIO4ALL you should then be able to see both interfaces under Cubase/Protools.