Bought this one after I returned a corsair TX750V2, which was returned due to the loud noise it made. The first thing to say about this is that the packaging is excellent. You get a case to hold all of the spare leads that you might or might not need. Doesnt come with a UK plug but thats no big deal as I have loads of 3-pin kettle plugs around. Being modular it is excellent for cable management and the inside of my Corsair 550D looks a lot neater than with the TX750 and its octopus cables. Have had it on constantly for about 4 weeks now running an I73770k overclocked to 4.5ghz, a Zotac gtx670 AMP! edition card, Asus P8Z77-V deluxe board, bluray drive and fan controllers and i must say that I think the PSU is excellent. Its very, very quiet. There is a little switch on the back of it that lets you put it in "hybrid" mode. This is how i have it and it means that, up to a certain point the fans on the unit will be switched off. They will automatically switch on when the PSU needs to be cooled or when it is drawing more power (dont know the specifics). What i do know is that, even when gaming, or rendering videos I can not hear the PSU. I can now hear my graphics card which i couldnt hear before with the Corsair PSU. I have read reviews etc that say that it is Seasonic that made the internals of the TX750V2 so it shouldnt make a difference. From my experience, it certainly does. Very quiet, powers everything i need it to. Cant comment on the efficiency of the PSU as i havent had it long enough but will update the review if there are any nasty surprises. I doubt there will be though.
If, like I was, youre umming and aaghing about spending the extra money for this PSU then please dont. Go for it, buy it, you wont be dissapointed. In this case the extra price is definitely worth it.