I'm gonna give PowerColor a benefit of a doubt, and say they still make quality components. However, their PCS+ series isn't one of them. Their R9 290(x) PCS+ are notorious for performance degradation. I highly doubt this is just case of faulty bios, I think this problem goes deeper than that. This problem lies in their Q/A control, and their poor choice of components (made in China).
Anecdotes from other people in another forum:
"Hi Guys,
Just to let you know, I've received the updated BIOS for my 290X PCS+ from Raymond however it hasn't made any difference when it comes to performances. Basically my 290X PCS+ performs at the same level as my 290 PCS+ (verified by running 3DMark, Unigine Heaven, Unigine Valley).
Informed Raymond which reported to me that Powercolor is investigating the problem.
Cheers" -Schussnik
"290 pcs+
ran a few tests overclocked
12v drops 11.5v with load
1200-1650
valley 65.6 
3d11 gpu 16200
overclocking doesnt effect performance as it should. Scores same as old bios when oc'ed
i'm bored with these cards, super cooling yet doesnt perform as 290"-daymond
"Update:
Replaced motherboard
Clean install windows 7 64....13.2 drivers....system drivers...
FAIL
I am now pretty sure after 2 cards new Mobo+psu some cards are faulty. Both had hynix ram.
Do not buy this card unless you test before."-daymond
From Youtube:
"I just think the card that we had degraded for some reason very quickly"
www.youtube.com/watch?v=OD8hvKvdfdw&list=TLxg8ex2mWvNXaA_wuAegXnEXbtkct_IBo
I've ran benchmark test myself and can confirm this performance degradation. My Asus HD 7970 Direct CUII outperformed my PowerColor R9 290x PCS+ by a big fucking margin.
At Extreme HD Preset in Unigine Valley:
PowerColor R9 290x PCS+ (@ stock speeds of 1050 core/1350 memory)
- FPS: 12.7
- Score: 531
- Min FPS: 6.8
- Max FPS: 24.6
Asus HD 7970 Direct CUII (@ stock speeds of 925 core/1375 memory)
- FPS: 37.5
- Score: 1568
- Min FPS: 20.2
- Max FPS: 69.2
If you decide to buy a card from PowerColor I'd suggest going for the Devil 13 series, their flagship series of card. I willing to bet that's where all the quality components went to. As for myself, I'm back to playing on my HD 7970 again while I issue a RMA with PowerColor.