There was a guy I know that had an 828 or hd192 something… IIRC, it was a 2ru unit with level meters and such on it. I never heard it, but what he said, he bought an Apogee Big Ben and clocked his converters with it and he said it was a night and day difference. I know Black Lion changes some of the clocks in the units… So the clock option may be totally worthwhile.
Have you checked geatslutz?? I remember seeing a lot of folks that had their stuff modded by B.L and they all seemed happy.
Thats all I know… I used to have a motu 2408mkiii back in the day.
Why not email B.L. and ask for audio samples??
Lastly, I don’t think there will be a wow factor at first if you do get your unit(s) modded. I may be wrong… It will probably become increasingly apparent when you stack tracks that the sound has new and better qualities once the unit was modded.