Which SPI Host Adapter Works Best to Interface with an MCU Device for High Speed Framing with DMA Enabled?

Question from the Customer:

I am interfacing a TI MCU (TM4C129x series) with the Aardvark SPI/I2C Host Adapter configured to slave mode. The MCU is sending 10 bytes consecutively out its SPI port in a single frame forming a single message (slave select signal is asserted for the entire 10 byte frame). The clock rate is 2 MHz.

I have observe...