Wasn't the 285 actually slower than the 280?
Sorta, they traded blows really. The 285 was a Tonga architecture but the 280 and 280x were Tahiti. The 285 only had 2GB VRAM also but was a good bit more power efficient than the 280. The 380X is also a Tonga architecture card and more power efficient than the 280X but about even performance.
285 vs 280
http://www.anandtech.com/bench/product/1333?vs=1332
285 vs 280X
http://www.anandtech.com/bench/product/1333?vs=1041
7970/280X vs 380X
http://www.anandtech.com/bench/product/1495?vs=1592
380X vs 390
http://www.anandtech.com/bench/product/1495?vs=1594
The 370 is a significant downgrade from the 7970
http://www.anandtech.com/bench/product/1495?vs=1590