I'll commend on this thread only to keep it simpler.
elec999:
"Looks like I need to choose the right power supply now, either a Corsiar or Seasonic, deal done here."
Both made by Seasonic AFAIK. Explains why they are both so good. Corsair 450W VX-series might not be the best because it's fan will start ramp up rapidly after 200W mark. 520W/620W HX-series is notorious from both handling around 300W before any noticeably ramp-up and then starting to ramp up cautiously. I have not heard my HX520W ramp up at all.
Here's a noise graph from VX-series (includes HX and two S12 variants):
http://www.silentpcreview.com/files/ima ... _power.gif
Why VX started ramping up around 200...250 watts instead of claimed 400 watts may be ambient temperature and backpressure of the computer case or optimism. According to the article intake air temp to PSU was 31°C so that probably lowered the ramp-up wattage.
From that graph, Corsair branded Seasonics seem slightly superior to Seasonic branded Seasonics. Biggest difference among them would likely be fan controller and how high it allows wattage to go before ramping up. Linear ramp-up (ZM600, NX8060) or near-linear (S12-430) are noisier on practical loads (150...300W for quadcore system). But I guess that S12-430 may be better today. That was a 2-year-old review the result was taken from. It's probably revised by now. (But don't take my word on it.)
elec999:
"Also please remember this system will be my main computer, but also need seti 24/7 on it. Some overclocking would be welcome."
Since you intend to SETI@Home 24/7 and might want headroom for OC, I'd favour HX-series over VX-series. Some recently revised series of S12 might be good too.
elec999 [in a PM]:
"It looks like I will be getting a Noctua NH-U12F for the Ninja to cool the psu, and undervolt it using a Zalman fanmate" [quoted from PM]
Noctua NH-U12F refers to a heatsink (with included fan), not to Noctua's fan. They make the fans themselves, unlike most heatsink manufacturers.
Did you mean you'd get the same type of fan supplied with NH-U12F and attach it to Ninja, or did you mean that instead of buying a Ninja you'd buy a Noctua heatsink+fan?
There's one reason why I'd recommend a non-Ninja, or at least not Rev.B Ninja (older revisions of Ninja are better): it's the socket775 mounting equipment. They use the same push-pins as stock Intel coolers. But do remember than weight of all big heatsinks (Scythe, Noctua, Thermalright) is way bigger than maximum recommended heatsink weight as defined by Intel. At least the very least required is to offer some kind of bolt-through equipment and backplate to minimize the effect of overweight HSF. This is exactly what Scythe removed from Ninja when it presented it's "improved" Rev.B.
You can buy Ninja for 60 eur, throw away Scythe fan, buy a Noctua fan for 20 eur and attach that. Or you can buy a Noctua HSF with same fan for 60 eur and save approximately 20 eur in total. Alternatively if you some day want to do some (heavy) overclocking (meaning, heavier than 3.2GHz) you might consider Thermalright U120E and pay 60 eur for it and since it doesn't come with a fan, buy a non-Noctua fan for it. (Remember what I said about Noctua fans only working well as case fans or widely spaced heatsink like Noctua's own or Ninja? U120E isn't like there heatsinks.)
"To cool the PSU"? Do you mean to cool the CPU or do you intend to do a fan swap of PSU stock fan to Noctua fan?
