As you can see from the bench contests we run in this forum, my cards are amongst the quickest reference 980s of the forum members here and AMDMatts cards can beat them in many scenarios.
I run with water and custom bios on my 980s and the 290X holds its own.
And so if they re-spin the 290X into a lower TDP card with 8GB of Vram it will place it slightly beyond the 980 (Non-ti) in terms of performance.
I wish the 290x were better. But from the benchmarks I've seen (e.g. LTT, DigitalFoundry), the 290x competes and is beaten by 970 at resolutions like 1080p. If it were better than a 970, then I'd expect it to overtake that card in sales considering the current price. I will admit, the 290x holds it's own at higher resolutions against the 980, as I've seen from benchmarks somewhere.
I wonder what magic AMDMatt did to get his 290x run so well? I hope the 390x does compete with the 980 and it comes at a similar price point to currently priced 290x (I've seen 8GB versions for under £300 at OCUK). If so, I may buy one instead of a 970, though I do hope MSI hurry and release an MSI Gaming 390x quickly following launch, since I don't trust reference coolers to run so quiet and I'm fussy with noise levels. Otherwise, it could mean bad things for pricing higher up the chain with the Fury X.
A lot of folks are saying the Fury X is out of league of the 980ti and is a Titan X competitor instead. But folks are forgetting that the 980ti is a TX competitor and is essentially a TX with half the VRAM at a better (but still unreasonable) price. If Fury X wants to compete price/performance, it needs to go up against the 980ti, which is better than the TX IMO. AMD are free to price it higher, if the Fury X performs significantly better than the TI. But given the rumored benchmarks, I doubt that'll be the case.
In any case, I'm looking at the £200-350 price mark for graphics cards over the next couple of weeks. If AMD give me better price/performance with a quiet air cooler than a 970, then they will get my money. Otherwise it'll go towards an Nvidia via a MSI Gaming 970.