thankyou for your help.
I made a little search. In my country (italy) I cant find all the version of R9 280x, I can't find the x-version of windforce (I don't know the difference)
On amazon.it i can find for example:
Sapphire R9 280X 3GB Toxic (PCI-e, 3GB GDDR5, HDMI, DVI, 1 GPU)
Sapphire DUAL-X R9 280X 3GB GDDR5 OC
Gigabyte Radeon R9 280X 3GB GDDR5
ASUS PCI-E A R9 280X-DC2-3GD5
MSI R9 280 GAMING 3G, AMD Radeon R9 280, 3GB DDR5
CLUB3D Radeon R9 280X royalQueen
Sapphire TRI-X R9 280X 3GB GDDR5 OC
GRA PCX GBT R9 280 3GB Windforce R2.0
Before this conversation, I would have bought the ASUS GTX760-DC2OC-2GD5 because I thought it was enough, and i could save some money...