I just got done with my latest mod and figured it's time to finally quit lurking around here share the love. My system is FINALLY inaudible at idle when I'm sitting at it with my headphones on (with nothing playing through them). I'm thrilled! This forum and the SPCR site have inspired me on more than one occasion.

It's not the greatest, but I like it!

Update:
I guess it was too quiet and not cool enough I had to undo the mod and put the original fan back on. Load temps skyrocketed beyond 80C in a heartbeat.

Clean up your cabling man!

You can see in this pic that it's not nearly as bad as it seems from a dead-on side picture (and, believe me, I know it doesn't look great). Unfortunately, based on the plugs in use from the PSU, the position of the devices they power, and the effectively non-existent "back-side" of my 1st-gen P180, I don't really have many options for cable routing outside of "roping" them all together to keep them out of the primary air-plenum. I actually JAMMED my 24pin cable between the case's backside door and the interior chassis since it was the one thing that was constantly in the way of everything. Behind the GPU in this shot you can see where I even hand-cut the lines on the ribbon cable that goes from my X-Fi to the 5.25" audio bay in order to reduce the space it takes up.

TL;DR: It's ugly as sin, but it's not as bad as it looks at first glance

I've seen worse (for airflow) cabling in a P180, if its ugly and it works - who cares?

I'd consider replacing that HSF completely, those zalman coolers are not wildely known for being silencer-friendly...

Some would say messy cables hinders airflow. I spent some time making a tidy job on my build, I do think it helps a bit..but then I had mostly flat modular cables which is useful.
As long as most wires are tied back out of the way it's fine.

I really like my CNPS9500, it's whisper quiet unless it's cranked up good. I cannot say the same for the CNPS9700, that thing is obnoxious. I tried replacing the fan, since it's the one remaining source of annoyance for me in the entire machine but the replacement just wasn't pushing sufficient air when the system was under load. I had, up to that point, never touched the Zalman cooler while the system was operating and ever felt anything more than above-room-temperature warmth. With the SilenX fan on there, the edges of the fins were hot to the touch and I could feel the heat radiating off of it. System hit thermal overload and shut down on me inside 30 seconds under load.

It's likely that I'll just replace it with a closed-loop liquid cooler, but I'm also up for suggestions for air coolers... It's a serious pain in the rear (and the hands) to work inside the P180. I like those massive Noctua units but I don't know how I would go about installing one without totally removing my mainboard from the case to do it (I really don't like that the 1st gen P180 has no cut-out on the back of the mainboard but, oh well).

Have you thought about creating an air-channel with a whole fan mounted to it for the Zalman cooler? You will have to plug the central channel with some foam in order for the air to actually pass through the fins. Might be worth a try.

Make some All you need is a drill, a hacksaw and some sandpaper or a file. Alternatively a nibbler-tool would do as well.