seasonic

What is the difference between these seasonic models? SS-520GB Active PFC & SS-500ET Active PFC & SS-500ES Active PFC totally messed up.

Which is the best for the money? Seasonic S12D 850W Corsair TX850W Corsair TX850 V2 Other(please specify)

AMD Processor Phenom II X4 955 - Model HDZ955FBGMBOX @6.5 Asus 870 Chipset AMD Motherboard Modal -M4A87TD @5 Corsair DDR-III Memory 4GB [2GB x 2}- Model TW3X4G1333C9A @2.4K Western Digital 500GB SATA 3.5" Internal HDD - Model WD500AADS @1.8K Logitech G1 Gaming Keyboard and Mouse @1.3K...

I need a new PSU. Seasonic s12II 520W or Corsair vx550 I'm having a bit of trouble deciding between the 2. I am not able to find the exact specs of the seasonic as some places i find that it supposedly has 3x12vrails@18A and in some places it has 2x12V rails @20A...