Sorry for the lag in response time... for some reason I wasn't subscribed to the thread...

anywho, DJ, I've run mine with passive cooling before too (for very, very limited amounts of time- just enough to swap fans) and with a slower athlon it probably could be done, but i doubt it's a good idea for extended operation. Mobile athlons (and laptops in general) run considerably hotter than I like my computers to be running at- hence the 6.75" rotron that cools mine.... I'll bet that your case is well ventillated tho, if you can run a 1600 w/o a fan for that period of time, I'd expect that it would have to be. If you want a quiet, fast system, you want a big case, and a TMD cpu fan, attached to a Thermalright SLK-700, SLK-800, SLK-900, or SK-7. the problem with mid-tower cases is that hot air rises, and unless you have a blowhole or a power supply with one fan and no bottom vents or a front mounted intake fan (like those Leadmans), it tends to get stuck at the top of the case, because there's nothing there to take it out. That's the problem I'm running into with my SLK-3700AMB right now- that case has 90cfm coming in, 150+ going out, and I can't keep my ram from getting near burning hot, and it's not running near stock voltage or speed- it's rated for 200MHz @ 2.8v- it's running 166 @ 2.6... with a full tower, this isn't a problem, because the heat can get well away from the motherboard, where it's usually pulled out by another fan or two...

The TMD fans are near-silent, even the high speed model, and they both move more than enough air to keep an athlon reasonably cool, especially with a good heatsink. Keep in mind that the retail heatsink on the new AMD barton chips is an Ni plated AlCu soldered or skived-fin hybrid cooler with an 18cfm Delta fan. they include those with the 2500s and the 2800s at least, and I'm pretty sure they include it with most or all of their other cpus now too. So, if 18cfm and an aluminum-copper hybrid heatsink can keep it within operating temperature, 27-35cfm and a solid copper heatsink ought to be more than sufficient.

I'd suggest a Thermalright heatsink and TMD fan, as mentioned above, along with one of the Chieftec/Antec/Chenming mid-towers or full towers, equipped with either adjustable fans (which I'd recommend, because you get to decide how much noise u want) or Vantec Stealths, Papsts or Panaflo low-speed fans...