As far as I know, Apple are the only computer manufacturer that publishes accoustic performance data based on the ISO standard and that data supports anecdotal observations that the Mac mini is very quiet. I used my daughter's 3 year old i5 based Macbook over the weekend, and it had no problems playing the websites that cause my AMD E450 problems. It appears that for whatever reason the AMD apu is loading the work entirely onto its puny cpu while pretty much ignoring the half decent gpu.
I shall wait to see what the autumn brings by way of a mac mini update (if any) at which time I'll look again at the other i5 based options out there. It seems a shame that Intel et al appear to be sacrificing cooling/ fan noise in the race to be small in the small form factor segment.