I'm still just a classical piker, so I'd never heard of this piece. It's not in quad, exactly, but wouldn't it be great if it were?
Helikopter Streichquartett (The Arditti String Quartet Play Stockhausen) – Berkshire Record Outlet (broinc.com)
It's a DVD, humprof, so who's to say it's not 5.1? For $5.99, why NOT?