Are you aware that there are already more powerful tiny ARM single-board computers on the market that fit in the same size, power and price envelope? Like ODROID: http://www.hardkernel.com/main/products/
From $35 4x1.5Ghz Cortex-A5 ODROID-C1 to $99 octa-core Exynos5422 ODROID-XU3 Lite (4x1.8Ghz Cortex-A15, 4x1.3GHz Coretex-A7, plus OpenCL 1.1)
They have their own ecosystem and monthly magazine (sic!). Raspberry Pi is one of the first and most popular; it's great for beginners, but if you really need to push the envelope there is always competition that tries to undercut them in price, performance and/or features. Now again, RPi 2 has set a new bar, but it is not that high.