A BRC is the "Big Remote Controll" for ADAT. It's the only way to get external sync (SMPTE) into an ADAT. I'm retiring one my self as I don't think it plays nice with my HD24.
On editing software, you can definately use Cool Edit Pro or any of the many multitracker/editors out there. We could all argue the various strong points of all the different ones out there but they're all decent and will do the job. I've used Cool Edit but I think Vegas is easier and more powerful. I think Cakewalk is even a little better and I'm thinking seriously about moving to Sonar. Just my humble opinion.
On sound quality, very subjective again. I think they sound great. There've been albums made on the old black faces and the type II's have even better converters. If you go to the www button right underneath here and go to my NoWhereRadio set up and check out Back At You. It was tracked in the basement to type II ADATs (two of 'em) and mixed thru an analog console. Granted the MP3 encoding is going to skew the sound quality a bit but you get the general idea.