My primary reference is the St. Petersburg Quartet (there was a box set for a while but it's gone now, I think). Listened to selected movements from a bunch of different sets before settling on it as my primary one. I liked the Pacificas as well but not enough to buy them; I do also have the Taneyev Quartet, Borodin Quartet III, the Emersons from their cube, and the Sorrel Quartet, which was my second choice during the mass comparison. Plus a few individual recordings.
I do not generally find my own tastes in accordance with the majority of forum-goers in this matter; I don't think Borodin II is that great for example (prefer Borodin I and III, although never acquired the former), and likewise found St. Petersburg and Sorrel, despite occupying opposite ends of the cold-warm polarity, to beat out most of the other competitors in terms of intensity, which is often the very thing people cite as what those two ensembles don't have enough of.