After doing some digging, it looks like there is really only two new GPUs being introduced here, which are the Radeon R9 290X and the Radeon R9 290. These look like they will have 44 and 36 CUs respectively (or 2816 and 2304 unified shaders) based on leaked specs. As for the rest, they're just rebadged parts from the 7000 series.
The R9 280X is a Radeon HD 7970 (32 CUs, 2048 shaders).
The R9 280 is a Radeon HD 7950 (28 CUs, 1792 shaders).
The R9 270X is a Radeon HD 7870 XT (also referred to as the 7890, 24 CUs, 1536 shaders).
The R9 270 is a Radeon HD 7870 (20 CUs, 1280 shaders)
The R7 260X is a Radeon HD 7850 (16 CUs, 1024 shaders)
The R7 260 is a Radeon HD 7770 (10 CUs, 640 shaders)
The R7 250 is a Radeon HD 7730 (6 CUs, 384 shaders)