Also, does your method require make-up gain (i.e. running the summed XLR outputs to pres then to the A/D)? That would be cool....
I have to say, I am pretty embarassed at charging money to put resistors in a cable, but other people don't seem embarassed by charging five times as much to put them in a box (OK, with pretty switches, etc) . . . and then you'd still need to buy the cables!
edit-- I see; you need to use either a BTA or some inline pads if you want to run them into mic pres? So, if you were summing four stereo stems/busses, you'd need two Mix-4's, which could be run directly into a converter (with an XLR to TRS cable or adapter if required) and if you wanted to run the Mix-4's into mic pres to color the sound, you'd need either the BTA's or a pair of 12dB pads. Is there a loss of fidelity or increased noise by doing that? It sounds like the BTA might be less noisy?