I got my home-built to be more quiet than the Dell they gave me at work... (I've got an Athlon 1.4, a 400W Antec PS, and a Gainward GF3 ti200)

1st step: ditch the noisy case fans. I purchased a pair of these for that: http://www.siliconacoustics.com/panfbl08a1.html . They push as much air as any other 80mm case fan I've ever seen over the years, and they are nearly silent. I have two of these pointed out the back of my Antec 840, and have no issues at all with case temps.

I actually bought 3 of them total, and pulled my existing power supply out to put one of those into that as well. Being careful of capacitors and etc, it was really pretty easy to do. Once I quieted the case fans down, I was glad I went for the third fan for the P/S.

Next I realized how unbelieveably loud my CPU fan was. As an Intel guy, you may not know of, or be able to use some of these items, but I had a Thermaltake Volcano 5 with a 60mm fan on my chip. Sounded like a small jet engine, once I was now able to hear it over the case fans. I purchased a Thermalright http://www.thermalright.com/ax7.html AX-7 for my heatsink (set up for an 80mm fan, to get the same airflow with lower fan speed). Combined that with a variable speed YS-Tech 80mm case fan (got everything from Newegg). I can turn the fan down while I'm surfing, for again practically no noise. Or, I turn it up if I'm ripping CD's or playing games. Even turned up, it's much quieter than my previous setup, and cools better as well. There's a variety of software alarms that beep at you if the chip starts to get hot, so I have little concern about forgetting to turn the speed back up. I'd like to automate the fan speed according to chip temp, but haven't figured out how yet.

I'm planning to get one of these for the chipset: http://www.siliconacoustics.com/aavidpassive.html, because having a fan on there is just silly I think.

My video card cooler is actually really quiet, so I've never been concerned about it. I'm not sure what you'd do there. I suspect the Zalman you pointed out would be fine at stock core speeds.

Right now the whole deal is very quiet, and even what you do hear is a low pitched, air movement kind of sound, not the high pitched whining and rattling there was before. I'd like to also get some damping material for the inside, but the recent changes have been so effective I've stopped short of needing to even bother. I use my PC to play DVD's on my TV, so it's in the living room. I don't even notice it's on any more.

Right now one of the main openings in front of the case is in front of the hard drive stack, so I fell like I'm doing fine there.

That's what I did anyway. Right now the loudest thing on the PC is - well, nothing stands above anything else. When a CD drive spools up it's far and away the loudest part at that point, where before I barely even noticed it. Overall the 3 Panaflo's in the case, and the heatsink I got (with the variable semi-quiet fan) made a huge impact. I'm happy...

And I love my AMD!