I'm in the market for a used ATX PSU to replace a noisy mATX one in my parents s775 system. Perferably one that uses a 120mm fan and takes well to fan swaps. I've heard about some FSP units being prone to failures, what are some reputable brands/series?

I looked through used PSUs on eBay a there were mostly FSP's between 250-350W in my desried price range with a 120mm fan. Am I a fool to disregard PSUs with 80mm fans?

What case is it. Sounds like you have an Micro-ATX case that takes an ATX PSU?

Antec Sonata.

How about the Seasonic X-650 of one of its family. Unless you get up to about 200 watts the fan doesn't even turn on.

I would not recommend you buy a used PSU. The main issues are that capacitors age, and you may also find that a replacement fan is required either immediately or not long after purchase. There are some quite reasonable budget PSUs around which may be a better buy. Komplett for example has the Fractal Design Integra 400W PSU for around 370 Krona http://www.komplett.se/k/ki.aspx?sku=597506. A new PSU like this would I guess meet your parents needs, has a modern spec including a 120mm fan and comes with a warranty. There is a review of the Integra 400W here http://www.sweclockers.com/recension/12226-nataggregat-i-budgetklassen-2010/11 which suggests that this PSU is both efficient and fairly quiet.

Hi, not sure where mATX comes in as the Sonata is an ATX case, which is good as means have huge choice of PSUs.
If you you can get it and budget stretches to it I would look to Be Quiet! 350 gold.
This should be efficient, high quality and quiet PSU that's fit n forget.
As a cheaper option I used a ColorsIT Black Edition PSU in an i5-650 + GTS450 system I built a while back and not heard back of any issue. Not the quietest by any means but a definite cut above the cheapest junk PSUs while being fairly low cost. Should respond well to a fan swap, can't remember which model I used, 450w I think, or if it has any fan control. Example of 480w model.

You don't mention what the system spec is but I'm sure quality 250/300w PSU would be enough. I have run my rig off a Seasonic S12II 330w, stressed and pulling ~320w from the wall, ~280DC from the PSU and was fine!
80mm fan PSU not necessarily bad, depends and the implementation, they will contribute less to case cooling but that may not matter. My PSU has (swapped) 80mm fan. Idles <600rpm and loads 800~1000rpm...

Seb

Sounds reasonable to buy a new unit, total price would probably be the same after a fan swap on a used unit. Still I don't like the rpms reported, makes my previous silencing efforts moot(used to be my old system).

I have a spare 1900rpm S-Flex and right now I can get a a Corsair VX450 and Seasonic S12-II 500W used for the same price as the Fractal unit. Whaddya think?

A used PSU by Corsair or Seasonic could be a better bet. But there is still the issue that you could end up paying around 50% of the cost of a new unit for a PSU of unknown history, future reliability is anybody's guess and there is no warranty. On that basis a new budget PSU would be a better buy. A factor here could be what makes and models are available in your locality, so you may be able to find a quieter PSU than the Fractal for around the same price or not much more.

I've decided I'll donate my VX450 to my parents PC and get a modular replacement for my own PC.

For a replacement I'm looking at the Antec High Current Gamer 520, based on price avaliablity and this nice looking fan graph:

Should be awesome after a fan swap.