AMD's Titan Killer is R9 290X
Nvidia only has GTX Titan Ultra to respond! Thank AMD for bumping the prices down to a reasonable level with the AMD 7990 at $699! The other new thing with the R9 290X you will find unlike with Nvidia's Titan is custom PCB's and overclocked variants.
R9 290X will cost in the $600-800 USD range, depending on the type of card, and will outperform the GTX Titan (2688 cores) stock per stock which currently costs $1000-1100 USD.
The GTX Titan Ultra (2880 cores), launched shortly after AMD's Hawaii GPUs, will cost $800-900 USD and the regular GTX Titan will have its price dropped to the $600-800 USD range.
Nvidia's REAL Flagship will be the GTX 790 (4608 cores) which will sport two underclocked GTX 780s and will still hold the $1000-1100 USD position. AMD will fall behind only in releasing their Dual-Hawaii R9 Flagship to counter.
Who will Be King? You Decide!