I don't know how to grab quotes, so I'll just go at it. I certainly didn't expect a consensus here (hoppedup). I'm a relative noob, but have read enough to know there are definite conflicting opinions and experiences regarding tascam vs. the world.
First, I want to thank you all for taking the time to respond. It truly has helped me better understand my options and question my motives. As many suggest, I am looking at the dr 680 because of "one box" multi-channel option for the price (expecting to not get a lemon), and my familiarity with tascam. My dr-60 has been flawless in its operation and durability so I know no negative issues with performance or tech support (knock on wood). I just got the sony pcm-m10 from the Yard Sale and now have to read another manual and figure out a new user interface. Would have preferred the dr-2d but none were available at the time.
Secondly, and to your question Gutbucket, I prefer the depth (to my ears) a second pair of mics adds to the performance. I also want to experiment with large diaphragms multi-pattern mics (possibly at4050). May use them as stand alone in the right environment or as split omni on stage if I get the chance, or who knows. If I upgrade to another pair of small condenser mics I can run a pair in x/y and another in some other configuration. And if I spend my money on an upgraded set of mics I'm still in the same boat of needing as second set of preamps for the new mics.
Hell, I guess the most frugal thing to do is just buy an inexpensive dual channel phantom power unit and a great set of mics. I could then run both pairs of mics into my dr-60 and use the m-10 for sbd feeds. But man I want a big new recorder (the F8 is too pricey Acidjack). It seems like the natural evolution of a taper is to start with some small used gear, gradually expand into an unnecessarily large and cluttered quiver of equipment, sell most of it in the Yard Sale or on Ebay, and gradually mature into a high quality streamlined and lightweight rig. I think I am just taking my place somewhere in the early part of the middle stage of taper evolution. One day I may find myself in the enlightened state of Schoeps, SD MixPre-d, and just my M-10, like a wise old man.