i think the general consensus is that the Great River is a fantastic preamp.
part of the reason you don't hear as much about it now is that it is not brand-new.
FWIW Audio-Technica, when choosing a preamp to run their mics through for the demos on their site, chose the MP-2NV.
obviously they could have chosen anything.
they also used RADAR converters, which are thought to be top-of-the-line in many circles.
the consensus is that the Pacifica is a great preamp too, just different.
it is newer so there is more discussion regarding it.