which of these power supplies is the best:
Corsair Power Supply HX520 520W
Seasonic S12II 500W, HT, 12cm fan, 80Plus
Tagan TG530-U15 530W "Easycon Series"
Enermax Liberty ELT500AWT active PFC
Fortron 500W Blue storm II

Corsair HX520

All of those units except for the Tagan (listed in the next tier) are Tier 2 units known for quality and stability. Any of them (except maybe the tagan) would be good choices. I would also choose the Corsair just based on the fact that it has modular cables which will help with air flow in your case.

http://www.tomswiki.com/page/Tiere [...] ngs?t=anon

1. Seasonic S12 500
 
2. Corsair HX520 if you want a modular PSU. Made by Seasonic.

They're all good. The 520HX is the best of them.  
 
I'd also look at the PC Power & Cooling Silencer 610W.  
http://www.newegg.com/Product/Prod [...] 6817703005
It's $15 more than the 520HX at newegg, but it's a tier 1 and having one powerful single rail is useful.

Any of these is probably good. Best can be judged on personal preference. For instance, the Enermax Liberty is modular and some people like modular and others don't, but is a good PSU in any case. I'd personally pick the Seasonic or the Enermax, but its really a flip of the coin among the PSUs that you listed. The Corsair HX is good as well. These three are all tier 2 rated PSUs. The Tagan and the Fortron don't seem to rate as well.

 
The S12 has 2 rails of 17A each, while the 520HX has 3x18A. I'd still prefer the 520HX...

Another vote for the 520HX.....

 
 
That's peak amps not constant amps.  
 
The Corsair provides a max of 480w on the 12v rails. That works out to a max of 40 amps and that is assuming the 3.3v & 5v rails do not consume more than 40w.
 

 
Also made by Seasonic.

On further consideration, of the PSUs listed, I'd go for the Seasonic S12 and not look back.

thx

Maybe we should ask the OP about his config. What if none of these PSUs is powerful enough?
 
I still don't get it. Sorry, maybe it's too early and I'm still sleepy. Why is the S12 a better PSU than the 520HX?
So, the 520HX has at most 40A in reality. Since the S12 claims 2x17A, I assume it delivers 34A or less in real life. Wouldn't the 520HX be a better choice, allowing for more powerful video cards or more disks and so on? What am I missing here? Is the quality that different? I doubt that, since they're both made by Seasonic.  
I'm just trying to learn, help me...
 

 
I dunno, I'm with you. The S12 has 408 watts on the +12v rails which results in 34amps. The HX520 has an added 20 watts (big deal I know) and 480watt on the +12v rail to give it 40amps. Add on to that modular cables. I know which one has my vote.

and which one is more quiet

Based on these user reviews, the 520HX:
 
http://www.newegg.com/Product/Prod [...] 6817151034
http://www.newegg.com/Product/Prod [...] 6817139001