If you download the official miner, set intensity to 21, nothing else, you get good speed and rock solid performance, speeds as follows:
- Asus 270x - 3.5 Mh/s @ 59c
- Sapphire 270x Toxic - 3.6 Mh/s @ 57c
- Sapphire 280x Vapour X - 5.8 Mh/s @ 56c
- Gigabyte 290 BF4 Ed - 6.85 Mh/s @ 62c
People have been getting much better speeds pushing the clock up with MSI Afterburner etc, I've just been running my cards at default.
Hope that helps...
280x vapour should do better Ignition75. At least 6.5Mhs. If you have time to try the new 14.6 beta drivers, I heard that you even get to 7Mhs.