For those, who need comparison data.
version 7 speeds:
7870 - 95 sol/s
7950 - 145 sol/s
7970 - 165 sol/s
270x - 100 sol/s
280x - 165 sol/s
285 - 110 sol/s
470 4Gb - 155 sol/s
Couldn't be more accurate. You can add
290 - 200 sol/s to complete the list