Contrary to the fans included with PSUs, the fans you
can
buy separately can be silent, especially when downvolted
to 5V. So to ensure you don't
overheat a fanless PSU, which can happen if it's too hot,
it could be a good idea to mount a fan close to the PSU.
That was a bit unclear. If I've understood correctly,
fanless PSU's turns off if they run too hot, that's
why you might want to add a little bit of air flow
through it, especially if you run a hot CPU, etc. and
have no case fan.
This may be good advice, particularly if you live somewhere much
hotter than the UK. However, you needn't assume the cooling efficiency
is inadequate. Just crank the central heating up to something
a little higher than the hottest temperatures you experience locally then run
it under as heavy a load as you can for as long as you need to in order to
satisfy yourself that it's safe to use sans fan. Regularly cleaning the unit
should help too. The Silverstone PSUs all seem to have a single temp
status LED and I'd imagine you'd see quite quickly if it couldn't cope
with the conditions. You could abort as soon as the warning LED lit.
I recognise that a device need not be truly silent in order to be effectively so,
and perhaps taking such a risk is unnecessary, but I've bought a fair few
"silent" or "quiet" fans in my time that were nothing of the sort.
I've also had
lots of problems with fans that seem to have (or develop) defects that cause
noise so I'd rather just be shot of the whole spinny roundy horror show.
Granted, when you put your ear into the case from the outside, you will
probably hear some air-swushing generated by that fan, so it's not
completely silent. However, unless you mount your HD in rubber bands and
further put it in a super-silent highly isolated box to avoid the
remaining high-frequency blipps, a good 120mm fan running at 5V would be
extremely unlikely to be more annoying than the HD. (if you use a HD of
course)