my suggestion if you are looking for more inputs would be to sell the box you have now on ebay, and get something like a Delta 1010 or MOTU 2408 MKII.
I had the 1010 for a while...great interface, but upgraded because the MOTU has Lightpipe also, allowing it to be expanded to 24 inputs pretty cheaply.
yeah they run fine together no prob. just have to put them on independent, or in-synch (under the hardware settings, in the control panel) depending on what you want to do.
but its very easy to switch back and forth from the two or three
i use a 24/96 and a delta 44