I don't often say this dealmaker but have you thought of Firewire?
You have a macbook pro so one of these
http://www.soundonsound.com/sos/jan0...ffirepro40.htm
should do nicely (I know they missed FW off one mac, wasn't that one was it?!) You then just neded a Behringer ADA 8000 unit to give you 8 more channels and Bob's yer whatsit.
Thing is D, there is a very strong probability that Firewire will fade away in a few years time, usb 3.0 will be the norm on "cooking" grade computers and laptops and Thunderbolt on the top of the range PCs and macs (just as now where you don't see FW on most "office" grade computers) . But you are fireproof! You got the mac and so you are going to find FW kit at bargain prices.