I want to buy 7 rig for Scrypt mining

total 7 unit:

1 unit:
CPU: AMD FX4-4300 Quad Core Processor
Motherboard: AMD 990FX Motherboard with 4x PCI-E x16 slots
RAM: 8GB DDR3 Memory
Hard Drive: Kingston 60GB Solid State Drive
Case: BitFenix Shinobi XL Full Tower Case
2 x Powercolor Radeon R9 280X 3072MB GDDR5  = 2*700 KHash/s= 1400
2 x VTX3D Radeon R9 280X 3072MB GDDR5 = 2*700 KHash/s=1400
PSU: up to 1475W Power Supply
Total per 1 unit 2800 KHash/s

7 unit * 2800 KHash/s =19600 KHash/s

1 unit 2,360 Euro / 3,200 USD

IT is worth of it ?

Considering GDDR6 in summer/late 2014 ?

Calc: http://tinyurl.com/nlu9qlz

What is your opinion ?

Thx !:)