Hello,
you should consider that the fastest available CF-Cards are achieving write speeds of 20 MB/s, 10 MB/s would already be rather fast. The card shipped with Professional DSP Board is probably slower. You would have to downsize the AD clock considerably to capture AD data in realtime. In contrast, the SDRAM or SRAM memory supplied on the board should be able to work in the AD's 125 MS/s region.
A low-level interface to CF Card (read/write absolute sectors) isn't too complicated. Using the True-IDE mode, it is identical to PATA (or IDE) hard disk drives. You have to understand the ATA register and command structure to some extent to handle it. As far as I know, Altera has a NIOSII CF interface, but no FPGA "hardware" CF interface. There may be free cores on the internet. Altera recently published a MAXII CF+ interface design example. It basically does some address register mapping, but no translation of low-level storage media access, which would be the more interesting part to my opinion. The example uses generic CF interface mode (PCMCIA I/O mode) rather than True IDE mode.
Regards,
Frank