I would suggest BeagleBoard.
It has an excellent DSP (TMS320C64x) (
C6000 High Performance DSP - TMS320C64x DSP - TMS320C6410 - TI.com)
Features and description
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Features:
600MHz superscalar ARM Cortex A8 processor
Over 1,200 Dhrystone MIPS
Up to 10 million polygons per second graphics output
HD-video capable C64x+ DSP core
256MB LPDDR RAM
256MB NAND Flash
I2C, I2S, SPI, MMC/SD capabilities
DVI-D and S-video video output
JTAG
SD/MMC+ socket
3.5mm stereo in/out
USB 2.0 HS OTG
RS-232 serial
Description:
==========
The Beagle Board is an incredibly powerful single-board computer developed by Texas Instruments, featuring their OMAP3530 system on a chip. The board is supported by a large community and is designed with open-source development in mind.
The Beagle Board measures about 3x3" and has all the functionality of a basic computer. With its numerous expansion options, the Beagle Board can be used as the backbone for a large variety of projects. The OMAP3530 includes an HD-video capable TMS320C64x+ DSP for accelerated video and audio decoding, and an OpenGL ES 2.0 capable 2D/3D GPU. Video outputs can be provided by the on-board S-video or DVI-D (HDMI connector) outputs.
The board also includes an MMC+/SD/SDIO interface, USB 2.0, 3.5mm stereo audio in/out connectors, and RS-232 and JTAG connectors.
The board can consume up to 2W of power, which can be provided via USB or an external 5V source, via the on-board barrel jack. Because of the efficient power consumption, the board requires no additional cooling.