Thanks, Abula, for that info.
As I don't need a small form factor, and taking some ideas from Vicotnik's post, I'm wondering if this build makes sense:
standard mini-tower case that can accept a mini-ITX MB (~$50)
ASRock M81 or M85 ($70) (as reviews says ASRock MBs use less power)
i3-4130T (TDP 35W) ($135)
picoPSU 90-XLP power supply (~$50)
large fanless heatsink ($40) (which, I think, can handle TDP 35W?)
no graphics card
120GB SSD, 4GB RAM, Windows 8.1 (~$220)
If this makes sense, then two questions:
1. Some posts say that even if the CPU can be cooled passively, airflow is still needed to cool other components on the MB. If so, I'm okay with a slow turning fan on the heatsink. (My current i7 build has CoolerMaster 212 Evo with a Nexus D12SL-12 120mm fan, and the system is inaudible for my ears. My main interest in fanless is to eliminate moving parts -- but one slow moving large fan is an okay compromise.)
2. Minor: I haven't yet found a mini-tower case with a hole drilled for the picoPSU DC-in jack. Of course, I can drill a hole in the case, or in a rear slot plate, but I'd prefer not to. Are there slot plates available with a pre-drilled hole for this purpose?
Update: Found a slot plate here: http://www.mini-box.com/s.nl/it.A/id.438/.f