Brent,
I missed the fact that you've had your SF gear upgraded. Very sorry. Of course I withdraw everything I said about it since I haven't heard yours. Higher quality caps and power supply improvements would, IME with other preamps, make a dramatic difference.
That said, $10K+ is indeed the price of admission to the 2 or 3 best phono/line stages I've heard, and even that doesn't necessarily get you there. Not that you need to spend more, I just meant that I've heard many $10K and even $20K preamps that DON'T get you there. Your buy quality used and upgrade path makes great sense to me.
Unfortunately, with SUT's, about the only way to know if a particular LOMC will mate well is to try. You could always adust impedance with resistors either on the primary, the secondary or both. That's a lengthy process needing many resistors of many types to find the optimal setup. Been there, did that, much prefer the ease and sound quality from my high gain LOMC section. YMMV of course, especially with something as complex as impedance matching with an SUT.