I need to build a quiet PC for basic tasks: Office, web browsing, mail, looking at videos. The more demanding task is related to photo with Lightroom. No gaming; no overclocking.
I would be happy to have something with stopped fans during web browsing, and starting fans when the usage is more demanding.
My idea is to start on this basis: pentium 3430 (about 54W TDP ; should I also consider some AMD APU?), a 350W gold alim 5I'm in France and a dealer sales rebadged seasonics), 8 Go of Ram, a 120 Go SSD and a 2 To WD green HDD.
Welcome to SPCR.
Pick a Pentium G3420: it's just 100Mhz less than a G3430 but it usually comes for 20-30 euros less also (using idealo.fr I see 55 euros for a 3420, but 78 euros for a 3430).
The only weak point of the entire Pentium lineup is the relatively basic GPU: a Core i3 is to be regarded as noticeably better, with reference to video and transcoding, but you may add a discrete graphics, if you ever should need, I guess. A discrete graphics is needed if you work in Lightroom with a wide-gamut 30-bit color monitor.
About the SSD, several SSDs don't like to be filled up, performance wise. So, even if some 120Go models aren't bad at all (as the Intel 530), I would advice to pick a larger one (as a Crucial M500 240Go, or a Sandisk Ultra Plus 256Go), or one which has greater performance consistency, like a Sandisk Extreme II, or a Corsair Neutron/Neutron GTX, or even a Seagate 600/600 Pro. Some mid-to-high-end OCZs (Vector 150, Vertex 460) and Intels (730, S3500 and above) are extremely good too in this respect, but just to be fair the firsts are often regarded as a bit less reliable than other brands, while the latters usually come at a premium over the competition.
About the RAM quantity, it mostly depends of images size: 8go are almost always fine, but it you're used to work with very large RAW files 16Go are a better option, if you can afford it. Use a low profile, low voltage dual channel kit: timing is not that important, 1600MHz is plentiful of bandwidth, I guess SPCR reviewers uses Kingston LoVo, several co-forumer Crucial Sport and Sport VLP, I think both are fine choices.
1) I really need help for the case. I consider either a Cooler Master Elite 130 (nice for the volume) or a Cooler Master Silencio352. From silence point of view, can I achieve the same performance with both cases ? What would you advice ?
I second most of HFat advices on that. I think that a small enclosure puts some severe limitations on PSU lenght, heatsink height, cabling (which obstruct airflow), so I would rather something larger. If you like the "cubic" style, one of my favourite is the Cooltek W1, but at first glance I see it's noticeably overpriced in France (30% more than in Germany and Italy). With reference to the enclosure, I think it also matters the buyer attitudes, I mean whether you are used to tinker with parts or not.
2) Are there some specific criteria to consider for the mobo related to the silence target, that would not be available on all Mobo ?
At least 3 software controllable fan headers, possibly some heatsinks on the power circuitry, lots of flexibility in the HW Monitor section of the UEFI/BIOS.
I think an ASRock H87 Pro4 (M or not) should be enough cheap (even if I see it's about 20% more expensive in France, than either in Germany or in Italy), and enough good for the money, but check the relevant manual online. MSI G43-series is also a fine choice.
3) Could a AMD APU (TDP of 65W instead of 54W) be OK to consider, or it would be more difficult to manage from noise point of view ?
IMHO an AMD APU should not be preferred over a Pentium: surely, it has a better stock graphics, but you will loose too much in efficiency and computational power. With reference to noise, there's no difference to manage an AMD or an Intel unit, giving the right (large with a slow fan) heatsink.
4) Which CPU fan would you advice for such a configuration, budget wise ? This one
is among my preferred coolers for such a setup: relatively cheap and with a good sounding stock fan. Given that it's a tower heatsink, it requires some space, but usually less than most of the equivalent quiet coolers.
5) where to put extra 15€ to get more silence ?
Either on some Scythe case fans, if needed, or on a disk drive suspension like the NoiseMagic one.
Eventually on an Arctic Cooling Accelero S1 Plus heatsink if you go for a discrete graphics.