Oh, my other fans are already at 7V - the 92's are spinning at 1200RPM (instead of 1500) and the 120 is spinning at what I'd guess to be around 700-800RPM (that header does not report the fan speed for some reason). I can barely hear it when I'm in bed - no trouble sleeping at all (the GPU fan is also fixed at some 45%, pretty quiet).
I bet I could overclock it, but my goal is silence, after all
Checked out the X6es, but it's just not worth the investment
IMO. Though I should check for how much I could sell my X4 first..