Below is my HWMonitor output for this Version 2 (6 memory slots) Z400 running one X5690:
From BIOS: temps of CPU0 is 26C and CPU1 is 0. Ambient is 19C and Memory is 57C.
Also from BIOS: CPU0 fan RPM is 1266, Memory is 3210, Chassis is 1590, CPU1 is 0, chipset is 0, PCI is 0.
I don't have a PCI front fan in this Z400 because the video card is a blower type, exhausting the case in addition to the Chassis fan at 1590, plus the power supply adding more exhaust out the rear. I never see the power supply fan RPMs show up anywhere, by the way. "Memory" is actually my add-on HP 4-wire chipset fan, attached to the header you saw, and which I've posted about. I add in a Noctua 4-wire LNA (or better yet a Noctua ULNA which are hard to find) to that chipset fan I get from a xw6600 or a Z600.
You'll find your Noctua fan plan will go too slow if the fans are PWM (and they need to be to respond to the HP motherboard's feedback) because that will take the slow Noctua PWM fans and then the motherboard adds its HP PWM throttle restriction, and the combination is too much slowing down going on. Done that.
Keep going, though, because no one has ever fully figured out the HP cooling strategy. Personally I have found I get what I want with what I have posted about, and even have gotten some added 4-wire Noctua adapters from Austria to dink with. Nice people.
Front fan (if you want to add) is nice with a Noctua non-PWM 92 x 25 mm running at about 900 rpm, via 3-wire Noctua and three wire LNA or ULNA. Just use the first 3 pins of the motherboard header there. You can shave off the side ridge on the RPM sense side of the plug, or swap in a 4 wire plug end onto the 3 noctua wires with a "stunt" wire end in the 4th hole of the plastic plug. It holds on to that motherboard header better that way.