observer- are all your molex connectors tight or some fit loosely?
I forgot to express my condolences for the data loss earlier- my heartfelt sympathies.
I hope and wish no one has to go through it.
Well, i haven't said it's the "psu" yet.

BUt voltage stability and/or temps maybe an issue.
Not many i know have a 7200.12 yet but those few who do, haven't reported any temp or grinding/clicking noise.
All have decent psus and decent enough cases with hopefully adequate cooling for the hdds.
Seagates are know to exhibit that slight whirring noise, esp while seek but once it's an audible grinding, it usually due to a dying motor due to power fluctuations/excessive heat build-up/damage due to manufacturing defect or physical impact.
Meanwhile i am yet to unpack and install the new 500GB 7200.11 i got from rma since quite sometime now. :lol:
And there is no hard and fast rule who is more reliable.
Varies with the season and the batch/model of HDDs released.
As of now, WD is more vfm with it's 6400AAKS with 5 yrs warranty and not so noisy peformance.
Seagate chips are a bit down inspite of the faster 7200.12 due to the 7200.11 fiasco and drop to 3 yrs warranty.