The Sapphire Radeon R9 290X Tri-X OC is an excellent implementation of a custom design Radeon R9 290X. While it still uses an AMD reference design PCB, it improves significantly on AMD's two major shortcomings - heat and noise. With its performance BIOS active, the card is 2% faster than the AMD reference design because of its overclock out of the box. Memory is also overclocked, which boosts its performance some more. However, there are faster pre-overclocked R9 290X cards, but the performance difference to those cards is quite small. This makes the Sapphire R9 290X Tri-X 2% faster than NVIDIA's GTX Titan, but 8% slower than the GTX 780 Ti. While AMD's reference design card often throttles to prevent overheating, Sapphire's card does not, always running at full speed.
As mentioned before, the card uses AMD's reference board, but cooling has received a major overhaul. The card may not fit into smaller cases because Sapphire chose to use three fans in a dual-slot form factor, though, which makes the card 31 cm long. But this choice also provides more room for the cooling technology to improve temperatures and noise. Our tests had the Tri-X produce very good gaming noise levels that are slightly quieter than the GTX Titan and GTX 780 Ti. While the card is far from inaudible, it has still taken a big step in the right direction. Noise levels in idle haven't improved at all, which is a shame. Sapphire could have engineered an extremely quiet card for work in idle, which would have benefited people who do not game all the time and want their PCs to be as quiet as possible. Don't get me wrong, the card is quiet in idle, but it could be virtually inaudible. Sapphire decided not to use the dual BIOS feature for a performance/quiet BIOS combo, which means that user can't opt to run the card very quietly but with higher temperatures or with lower temperatures but a bit more noise. The ASUS R9 290X DirectCU II OC does have the option, and I consider it an extremely useful feature because it eliminates the need for manual fan control via software. But with only a single BIOS, the Tri-X's acoustics (37 dBA) and temperatures (73°C) are well tuned. I would have opted for slightly higher temperatures with less noise as there is a ton of temperature headroom to do so. Remember, AMD's reference design runs 95°C, which is perfectly safe. I think Sapphire tried to focus on lower temperatures to impress people who get scared by such high temperatures, though. The ASUS DC II OC with its quiet BIOS enabled is a better choice if you want the absolutely quietest R9 290X out there, and it even comes with that backplate Sapphire's Tri-X doesn't have.
GPU Overclocking ends up in the upper reaches of what we've seen on R9 290X cards. Memory overclocking works incredibly well because Sapphire used Hynix chips on their board, which significantly improves overclocking potential and helps avoid the stability issues some users with R9 290 series cards running Elpida chips are encountering.
In the US, the Sapphire R9 290X Tri-X is available online for around $700, which is a $30 increase over the current reference design price of $679. These price levels are clearly insane, and there is no reason to buy a 290X at that price. Only slightly more expensive, the GTX 780 Ti is much faster and comes with better power/heat/noise. The Sapphire Tri-X retails for €500 in Europe, while the reference design costs €445, which is a more reasonable price, and the ~10% price increase over the reference board is definitely worth it, without any doubt. If you were to ask me whether I would buy the Sapphire Tri-X or ASUS DC II, I'd still go for the ASUS card because it runs higher clocks, has a dual BIOS that includes AMD's quiet/performance mode, and is shorter, and it includes a backplate.