I don't know of any 2.4 gbps DES chips, but DEC has built a 1 gbps chip. .... Key-loading is a different operation, and that might not go nearly as fast. Any hardware assists (i.e., DMA) would be for the data, not for the next key to use on the same block of data.
Usually the limiting factor is examining the <ostensibly> decrypted data for statistically significant patterns indicating that you have the correct key. The fast DES chips don't help with this at all. A known plaintext attack, of course, doesn't have this problem, but these are probably of limited interest in real applications.
If you were interested in cracking DES, I wonder if you couldn't just build the hardware out of FPGAs. That way, you could make key loading and the decrypted data test fast as well. - Jay