I built a quiet PC a few months ago, and can vouch for the components, temps & noise level for anybody else interested in building a similar one. Here's the spec, along with today's prices and upgrades:
Chenbro Gaming Bomb / Xpider case Â£44
Nexus NX-3500 350W PSU Â£38 (Nexus NX-4090 400W Â£49)
Vantec PSU Dampener Â£5
Nexus Noise Absorption Material Â£23
Quiet Feet (medium) Â£8 (low profile Â£4)
Gigabyte GA-8TRS300M w/ ATI 9100 GFX Â£47 (GA-8TRS350M Â£??)
Intel Celeron 2.4 Â£47
Kingston 2x512MB DDR333 (transplanted)
Nexus RAMsink Heatspreaders Â£6
Scythe Heatlane Zen NCU-1000 (NCU-2000 Â£53)
Samsung Spinpoint SP1604N 160GB PATA (P80 160GB w/ 8MB Â£63)
SilentMaxx HD Enclosure Â£38
Plextor 4x DVD+RW (transplanted)
Black Spiral Wrap (assorted sizes)
Tom's Hardware recommended the Gaming Bomb. The price was reasonable, it wasn't too big (unlike some cases with removable trays), and it could take a 120mm rear fan and 92mm front if necessary. It came with nasty hard plastic feet, which caused horrendous resonance with my desk top. The Quiet Feet may seem expensive, but they made a big difference. (Tip: put electrician's tape across them in an X to stop them sticking to the desk).
The Nexus NX-3500 had glowing reviews, and positive feedback in the forums. It's well designed and built, and - though not silent - it is very quiet. Importantly, it had a 120mm fan. Some people have questioned the relatively low 18A available on the 12V line for high-powered CPU's (preferring Enermax or similar with 33A), but my first NX-3500 ran an Asus K8V Deluxe / A64 3000+ quite happily for months.
(Note: I always intended to have just one hard drive and one optical, to keep the noise down and reduce generated heat. So running a mid-range Pentium on a 350W PSU shouldn't be a problem.)
I originally bought a 2.5" Toshiba 40GB 16MB hard drive, principally for it's quietness. It was a great little drive, but a little low on capacity. Rather than upgrade to a more expensive 80GB model, I bought a Samsung Spinpoint 3.5" instead with twice the capacity at almost half the price. The Spinpoints are among the coolest running HD's going, because they only consume about 8.5W, as compared to the Seagate Barracudas' 13.5W - so it's less heat to dissipate.
I recently placed the Spinpoint (encased in a SilentMaxx enclosure) at the bottom of the case, because I couldn't find my drive rails at the time. As it turned out, this is a good thing. My other PC's Seagate/Spinpoint SATA drives are also in SilentMaxx's, but in the regular 5.25" bays - and they seem to run a lot hotter. I can now barely hear the drive defragmenting late at night. Do NOT buy the SilentDrive, which is rubbish. The SmartDrive 2002C would be a good alternative, but you'd have to import it.
Dtemp has never reported a drive temp greater than 35C for the encased Spinpoint PATA, which is good going during summer. By comparison, my Barracuda V SATA builds steadily up to a borderline 48C.
I chose the Gigabyte board over the similar Asus P4R800, as it came out slightly ahead in the reviews. Plus, it just looked better.
I wanted modern on-board ATI graphics, so it would have enough grunt for some light 3D work (not games) without requiring a separate GFX card - to save money and also improve airflow.
I was going to transplant my P4 2.4C Northwood, but thought it might run too hot. A customer review I'd read said the Celeron he'd bought ran fairly cool. Many forum messages debated whether this was indeed the case or not (being the same 130nm as a regular P4), but I think it's true. The BIOS CPU temp sits rock steady at 38C.
Unfortunately, I can't get a reading in XP, as none of the regular monitoring software works. I've tried Sandra, SpeedFan, Hardware Sensors monitor etc. but they all insist I have two CPU's! CPU1 always reports 25C, CPU2 74C idle, 94C load (which must be on-die or something). I've scoured the net looking for reasons why, and even written to Gigabyte technical support - with no reply.
Of course, there is a performance hit between the Celeron and Pentium, but not so you'd notice in general use. In SETI or Folding you would, but that's not what this PC's for.
The NCU-1000 had just come out at the time, and it was a bit of a gamble because many people doubted it was up to the job. (That's partly why I chose a Celeron 2.4 over a Pentium 2.4). I'm glad to say it's an extremely efficient device, and I've no doubt the new NCU-2000 is even better. It gets warm to the touch, but never hot.
I'm sure it could quite easily accomodate a faster Pentium, though there's no point getting one much above 2.8 as you'd never be able to use all that power for very long (without your temps climbing). The single 120mm fan in the Nexus PSU is situated immmediately above the NCU-1000, and does an excellent job of quietly expelling warm air.
Fitting the Nexus insulation material took quite a long time, but I sealed everything up as much as possible - including the 120mm rear grill, PCI slots, and unused 5.25" bays, to make sure it was drawing as much cool air from the front intake as possible. I definitely think it was worth installing it, even in a single fan PC.
The Nexus RAMsink heatspreaders weren't really necessary, but they did make the aging Kingston memory look more modern.
They were an absolute nightmare to fit, though!
I hadn't used spiral wrap before, so I was surprised what a difference it made. It not only tidied everything up neatly, it let me direct the wiring easier. There is no clutter whatsoever, and it only costs a couple of quid.
I leave it on during the day, but switch it off at night. I can comfortably watch TV from only a few feet away without being able to hear it. And it's plenty fast enough for every day general use.
You could save time - though not money - by looking at the new Nexus Breeze case (which admittedly uses two fans). It comes with the NX-3500 PSU, 120mm case fan and acoustic material already installed.
I'm now planning on modifying my gaming rig (MSI K8T Neo FIS2R, A64 3000+, Zalman CNPS7000AlCu, Enermax 465P) to have just two fans: one 120mm on a NX-3500 or NX-4090, the other a Nexus 120mm Real Silent case fan. I want to try running the NCU-2000 fanless heatsink while playing Far Cry and Thief. I'll let you know how I get on...