IMO the PSU is too noisy. Antec said it shouldn't be and adviced RMA, but it's older than 3 years so I think that's not an option. What's the best fan to use?
It's a 80 mm fan. I think it's easiest to let the new fan run at a constant rpm.

Actually, it might be easier to just use the existing fan header in the PSU. Is the PSU fan controller to the original fan rpm (curve) or is it smart enough to be able to handle other fans?
If not, what rpm should be the new fan be?

AFAIK it's just a matter of starting voltage and current rating (check the sticker on the fan to retrieve online the relevant data, if any): my R8 won't start reliably if feeded by the PSU header.

Some people had good results with EA500 using the Zalman ZM-F1 (don't know which version).

The existing fan is an ADDA ADO812HS-A70GL which is a sleeve bearing fan with a maximum rpm of 3200. So I would guess a suitable replacement candidate could be the Scythe Kama Flow2 80mm 2900 rpm model SP0825FDB12H. It has an FDB bearing which should last longer than a sleeve bearing particularly in a PSU, and is rated at 120,000 hours by the manufacturer. See http://www.scythe-usa.com/product/acc/108/sp0825fdb12_detail.html. The existing fan header in the PSU will be thermally controlled in some way, so the hotter the unit becomes the higher the fan rpm will be. I cannot find a start voltage for the Kama2 80mm models, but in practice the thermal control in the PSU will simply increase voltage to the point where the fan starts.

So, I bought a Kama Flow 2 2900 rpm, opened the PSU, tested the new fan on the PSU fan header, cut two tie rips / wire straps, unscrewed the top PCB, removed the old fan, put in the new fan, connected it, rescrewed the top PCB and tested it. Fan sounds comparable to old fan. :p
Are you sure the 2900 rpm model was the best choice? Maybe the min fan voltage of the PSU is too high.
So, I tried without fan: high-pitched electric / electronic noise.

I guess the only solution is a new PSU.

Hi, so even if you got a quiet fan in to the PSU it would then be making excessive electrial noise?
That's bad luck and as now mod'd won't be any warranty either. I would put it back together with original (or Scythe) fan and then use it somewhere noise doesn't matter or sell it on eBay or the like and buy a new one.

PSU whine is a bit luck of the draw and will also be strongly influenced by the system it's powering. I had a NeoHE that was lovely, till I put a GTX260 on it, then whined horribly. I had S12-II 330w power the GTX260 in a system fine, but swapping the GTX260 for a GTX285 made it whine badly.

For what it's worth the Antec Signature I have now seems to be free of whine whatever it's powering, so far....
I've not seen any reports of Enermax PSUs whining, the Modu/Pro82+ and Modu/Pro87+ have been revied by SPCR. The 82+ were very nice for their time but reports of fans going bad quickly. The 87+ looks excellent, 300rpm fan speed to quite heavy loads and 80+ gold efficiency, depends on your budget. The passive Seasonic X400/460 also excellent by all accounts and not over-priced, also worth a look at the higher X models, passive till need the fan to keep cool, then quiet.

Good luck, Seb

You could try coating the coils with hot glue. Another thing worth trying is disabling various power saving features in bios or through Throttlestop.

It was out of warranty (by 3 months) already. Otherwise I would've RMAd it.

The Pro87+ costs 104 euro (in NL). Signature isn't really available and Seasonic X is also 100+ euro.

I was thinking about a Nexus Value (52) or NX-5000 R3 (60). Bad idea?

Somebody?

The Pro87+ has a five year vendor warranty, and it is a much better specified PSU than the cheaper alternatives. Only downside is that this is the non-modular version, and I prefer modular PSUs to cut down the cable mess. But the Modu87+ is more expensive, so if you are happy about the fixed cables the Pro87+ is a good buy in my opinion even at a price of around 100 euros.

What about the FSP Aurum Gold 400/500? Or be quiet! Straight Power E9?
Both are 80+ Gold, have 5 years warranty (AFAIK).
Unfortunately not tested by SPCR.

Don't get me wrong, the Pro87+ looks like a great PSU, but I'm just wondering whether there are good alternatives.

The Straight Power E9 models from be quiet look to be good, if the specification is anything to go by. For example they have an 135mm fan but in the absence of reviews it is difficult to know whether they are as quiet in practice as the spec suggests. If you buy the Enermax you can at least be sure of what the actual performance will be.

Max rpm is 800 or 900 rpm, so I don't expect a lot of noise. I've actually got a 600 W be quiet in an older PC, but I don't know what model it is.
I think SPCR should review some be quiet PSUs. :p

Just got the be quiet! Straight Power E9 400W. Noise difference with the EA-500D is huge. :p