interface recommendations for Spectrafoo / Smaart ?

[runrunrun]

looking for a portable audio interface to take pink noise room measurements for FOH with Spectrafoo

will be using it with an audix TM1 for measurement and Spectrafoo

what is the cheapest worthwhile interface that will give good measurements?

i only need one channel analog I/O but two would be nice as well

i'm thinking something from MOTU / Presonus? any experiences?