Several listers mentioned the Arditti Quartet.

I had the great fortune to encounter, in Building 19 of all places, a
copy of the Arditti's eponymous CD featuring an assortment of selections
by Nancarrow, Xenakis, Ruth Crawford Seeger, Roger Reynolds, and (thrown
in for good measure as "proto-modernity") LvB's Grosse Fugue.  Amazing
technique and performances, of course; just to attempt to pull off a
Nancarrow piece just about says it all, the cross rhythms being too much
for mere mortals other than player pianos.  I espeiaclly liked the Seeger
quartet; she solved a number of compositional problems years ahead of many
better-known post-Schoenberg composers, and produced a marvelous piece in
the process.

It was said, by the way, that Elliott Carter intended for his fourth
quartet to be his last, until he heard the Arditti performing his work,
whereupon he decided to write a 5th quartet just for them.  (Too bad it
seems impossible to find all 5 Carter quartets in one collection
somewhere.)

On the topic of the Kronos quartet, I enjoyed their interpretation of
"Purple Haze".  I believe the other Hendrix work they tackled was "Foxy
Lady", which was considerably less successful - largely because the
original "Purple Haze" happens to be a wonderfully constructed piece of
music centered on a three-note rhythmic and harmonic concept; but "Foxy
Lady" is nothing more than a simple riff with a song built around it.
But I guess it took Kronos to demonstrate it.

Steve Bacher