I figure, at the very least, I'll have a recorder that will do the job for a good number of years. The Microtrack seems like a toy to me, I viewed the JB3 the same way. It's not Pro stuff.
If the ACM mod for the 671 is like the ACM mod in the 660, I know I'm going to like it. If for some reason I want to have a different sound, I'll get an analog pre to run in front of it.