Let me go looking, I'm only recently now getting r23 (and soon r14), and I have not had ethylene, with co2 I pulled -58C (stuck at the triple point it would seem).
As for quad core ready single stages, I'll post up results of Tyler dustins unit in the current page when I finish up tuning this week. The quad core discussion thread had the results of Harvsharks unit (With a SC12MLX) pulling -38.2C at 270 watts.