I would strongly lean toward using matched pres with matched pairs. Not having access to any pres other than my pair on my interface and also not having matched stereo mics, I have no experience other than being able to say using unmatched mics for a stereo image sucks, you have to mess around with the panning for AGES to get an even sound!

I haven't messed around much with trying to get a good stereo image with different mics, but I have recently purchased a set of NT5s and though I was using two different preamps, the results were stellar to my ears.
I could use two channels on my interface to experiment, but it would be nice if I could secure another/matching single channel pre and/or a nice two channel pre.

...aren't we talking elsewhere?

I'm typing into a box. What are you doing? :P

I like stereo. I like pairs of microphones. I generally purchase microphones in pairs. I don't necessarily have any "matched pairs" per se but when recording things in stereo, I try to keep some degree of consistency. So utilizing a stereo "pair" of microphones that are a reasonably close match to one another i.e. 414's, SM 81's, etc., screams for preamps of a similar family heritage.

Plus, you run into instances where your phase integrity could be compromised. For instance, I have a Roland M240, line level mixer. This cute little device is all single ended inputs. So are most of the outputs. That is with the exception of the one pair of Master balanced outputs on XLR. Where, on the back panel, it is indicated that pin 3 is high with pin 2 low. So quite contrary to what we all considered to be pin 2. However, not for Roland, they like pin 3 hot and pin 2 cold. Not exactly a new piece but was purchased in the 1990s. And you wouldn't want to deliver that kind of stereo recording now would you? Of course not.

Upside in downside out engineer
Ms. Remy Ann David