1) Have you read the P4 quieting article? Look under mods & projects in the main site.
2) Your mobo fan control interests me, Please remark with more detail here: http://forums.silentpcreview.com/forums ... php?t=2175
Is it adjustable via BIOS?
might be worth a risk -- Papst fans can often be "clickers". Otherwise, look for a Panaflo w/rpm sensing. Hard to find. Check posts in the fan area and see if there's any links suggested.
4) Sparkle - fan swap usually works well. Don't know about thermistor control -- usually if the PSU has it, there's some ref to it -- like noise blocker or something right on the PSU casing.
5) OCZ P4 eliminator passive heatsink -- Have a sample, no chance to test, but I doubt it can be run fanless. Fins are to short & don't look optimized for natural convection cooling. Depending on your case airflow, the Zalman 6500B-cu can be, but I prefer a 5V Panaflo instead of no fan: the latter can get tricky & the noise reduction is so miniscule.