Although HardwareSecrets found a number of Rocketfish PSUs that burned well under their labelled rating, that appears to be a newer one. I confirmed on 80plus.org that it is 80+ certified, which means it was tested at 100% of its label. You could safely run a HD7870 or even a HD7950 on it.
Yeah that seems to be the general opinion. While some Rocketfish can be janky this one has rather nice reviews. I've been running it for a year with no problems. I'll probably go with the Radeon 7950.