I can probably get there using one of my UI-24r mixers as they support 32x32 over USB unless REW requires that specific interface. I have a pair of the Behringer reference mics. They are actually pretty decent mics. I've used them for chorale, taiko amd ohd's. OHD... not my first choice.
REW will work with basically anything. It's worked fine with my QSC TM30Pro, and I'd expect the UI24R to work fine too. The mics will also do the job.
FWIW, if you pay for the $100 REW Pro upgrade, you get multi-channel inputs (with further features on their way). Set up a number of mics, and you'll get a curve for each position.
The free version has all the features apart from the multi-channel stuff, so stick with that to get started.
Chris