The Sapphire R9 290X Toxic is said to ship with a hefty factory overclock made possible by the custom designed vapour-chamber cooler with three fans. There is still no word on the actual clocks or price, but the card is expected to show up in a few weeks.
It won't come cheap, but then again it is supposed to take on Nvidia's new GTX Titan Black.
This will probably be the first consumer graphics card with 8GB of memory, but we're not entirely convinced it makes sense. On lower resolutions it certainly does not, but for enthusiasts with deep pockets and 4K/UHD monitors, it might make a difference.
Mere mortals with 1600p or 1080p monitors don't stand to gain much, unless they are using a multi-monitor setup. The same applies to Nvidia's Titan Black, with 6GB of GDDR5.