A silent PC depends on all components taken together as a whole. The thickness of the case does help dampen noise, but if you have noisy components then not matter how thick the case is, you will eventually get some noise.
The primary problem I see the the SilverStone LC02 is the 60mm fans. Small fans generally have to spin faster than larger fans to move the same amount of air. higher RPMs means more noise. The small PSU that comes with it will also have a small 60mm fan which is another source of noise.
Of the three HTPC you have listed, I would have to say the most attractive looking is the Moneaul 972B. However, all three of them use 80mm exhaust fans. Not as bad as 60mm fans, but generally not as good as 120mm fans. You can always search for quieter fans if the ones included are too loud. The LCD screen is nice to look at, but I don't find it to be very functional for my tastes and while it is something I can afford to buy, an HTPC case isn't something I want to flaunt.
I use the SilverStone Crown CW02 case for my HTPC:
1. Thick case 0.8mm or 1.0mm of aluminum (can't remember exactly).
2. 120mm exhaust fan. The default fan is pretty quiet, but I'm considering installing a replacement.
3. Able to accommodate a full size ATX motherboard.
4. Has the capacity to install up to 6 hard drives.
5. Optional 92mm fans can be installed underneath each of the two hard drive cages. I purchased two quiet 92mm fans to cool my hard drives (Scythe fans), but it's a trade off. Better to have a little bit of noise than to loose data on 6 hard drives due to heat failure.
6. Tall enough to fit a large HSF on the CPU like the good 'ol Tuniq Tower.
The only bad thing about the CW02 is it is rather compact case for something that can fit a fullsize ATX mobo. If I wanted to install / replace a hard drive, I would need to remove the PSU on side, or the CPU HSF on the other side. Removing the HSF requires the removing the entire mobo from the case. It's not a case for the faint of heart, but I am pretty happy with it.
As stated before, overall noise depends on the components. Other components within my HPTC are as follows:
1. C2D E6600 that is being cooling by my Tuniq Tower. I'm considering disconnecting the fan to passively cool the CPU to reduce noise a little bit.
2. Passively cooled nVidia 9600GT.
3. One WD Black 320GB HDD, one WD Black 500GB HDD, two WD Green 1TB HDDs and two WD Black 1TB Raid Enterprise HDDs.
Regarding the PSU, I generally by Seasonic PSUs because they built high quality PSUs that are efficient and generally quiet; some of thier PSU models are quieter than others. I have an older S12 500w PSU in my HTPC.
Seasonic also build certain PSU models for Antec, Corsair and PC Power & Cooling.
thanks jaguar, i agree the lcd might not be of use. hence am considering the zalman hd503 or the silverstone crown CW02 as you suggested. again, key is silence. i wish there's a review as to how much db noise these two generate, as i would need to import one of these to my country ... and wouldn't want to make mistakes.
budget? nothing in particular, but not more than $3000USD, preferably much less as this htpc will be only for audiophile music and blurips (via harddrive/usb). i won't be using it to play bluray discs, as i have ps3 to do it. and for gaming, i have already bought a i7 system for gaming using nvidia 480gtx so i don't need it as well.
The SilverStone Crown CW02 is quiet enough for me. I have a little bit of ambient noise coming in from the street that helps other things in my apartment that makes noise; like my HTPC. If I disable the two 92mm fans used to cool the hard drives, then the HTPC becomes much quieter. Those fans are not necessary since not all 6 hard drives are active at the same time, but I rather be safe than sorry. What I'll probably do later is defrag all my hard drives one after the other, and measure the temp of each hard drive.
Since you are not gaming on the PC, then you should be fine with using WD "Green" drives since they generate a little less heat and noise due to the fact that they spin closer to 5400RPM rather than 7200RPM. Current 5400RPM hard drives are faster than older 7200RPM hard drives because of the data density on current hard drives. The WD "Blue" drives spins a bit faster than "Green", and lastly WD "Black" drives for the best performance, but more noise and heat due to 7200RPM speeds. I would go with a WD "Black" drive for the OS (faster boots), and all the others will be "Green" drives in your case.
Assuming you are not gonna be using your HTPC to encode video, you can buy a low power CPU like maybe a i3-540. I'm pretty sure that can be passively cooled by a "Tower" HSF. I would do a little more research on that just to be sure. Sorry, I haven't really researched CPUs since I bought my Intel Q9450. I don't need the temptation....
As for the video card, a passively cooled HD 5570 will get the job done. However, there are passively cooled HD 5750 (and HD 5670)if that pique's your interest. But the HD 5570 is perfectly fine for video playback.
As for a PSU, I recommend Seasonic PSU all the way (they also make some models for Corsair and PC Power & Cooling). I haven't done much research since 2006 which was the last time I had to purchase a new PSU. Seasonic is known for high quality and very low noise PSUs. I suggest:
If you buy the SilverStone Crown CW02 and all the components I recommend (excluding the optional 92mm fans), then the HTPC will only have two 120mm fans making noise. The Seasonic's fan and the exhaust fan the comes with the case.