AMD APU is an obvious cost effective choice, 14nm too, and a mid-low end Polaris GPU in that APU could be a slightly more expensive choice at first, but more cost effective later and giving NX more longevity, so more sales.
The only part I doubt about is Zen, if the rumours are true, NX would use ARM, so either an AMD K12 ARM CPU or a third party licensed one.
An APU with Polaris GPU and ARM CPU would be very cost effective, and, thanks to using one of the latest ARM implementations, smaller, cheaper and less power-hungry than a x86-based one with the same raw performances and same production process.







