Well, I have a PooperCrapper R9 280x, and judging from my Fitestrike mark, and other peoples Firestrike mark that also have a PooperCrapper, it performs poorly, even OC'd to 1200/1600, I'd easily say it's around 15% under performance range from the top tier cards. I bet the lesser models such as R7's would be even worse.
PooperCrapper are cheap for a reason, their cooling isn't the only thing that's subpar, they've even been known to put in half the bus lanes needed for the bit rate in cards years ago.