1) Sapphire Radeon R9 280X Vapor-X OC 3072MB
Core Boost: 1070MHz, Memory: 3072MB 6200MHz GDDR5
11221-02-40G

2) Sapphire Radeon R9 280X Toxic OC 3072MB GDDR5
Core Boost: 1150MHz, Memory: 3072MB 6400MHz GDDR5
11221-01-40G

3) Sapphire Radeon R9 280X Dual-X OC 3072MB GDDR5
Core Boost: 1020MHz, Memory: 3072MB 6000MHz GDDR5
11221-00-20G

what will be good ? want to buy 4-6 per MOBO I must calucalte how to manage
28-32 GPU....