Eh- I just finished learning just about everything I can about the 671, dunno if I'm ready to start all over again with another box. Besides, I really like the 671 a lot. If I'm gonna go with an all in 1 (and at this point it looks like I am), I'd prefer an ACM 671. Also, with the 671 I retain the option of running an outboard pre/a>d.
I think after this Biscuits run I'm gonna send both boxes to Doug, get them checked out (figure out why there is such an issue between the UA5's coax out & 671's coax in), and have him mod the 671 at the same time. The option to run T+UA5>671 or mics>ACM671 is pretty nice, and not a big deal price wise.