Hello Thomas,
I dont know much about CF card etc, but I can give you some information on microcontorllers and sources.

The Philips P89C51RD2BN (NOTE: extension BN = programmable clock speed) if used with a 20MHz crystal with x6 mode you will get 300nS, this chip is available from Elektronica Sales, Chennai-India, cost is around Rs.150/=, you can also get the P89C668 it has 8K internal xram.

With C8051F020 mentioned by Mike, you can expect 40nS speed, I purchased these for around Rs.1200/= now they are available for around Rs.750/=, the dealer is in Bangalore - M/s Hynetic.

Since you are also discussing USB, Cygnal has come out with some USB with 8051 core, these are again available from Hynetic.Find out more about it from Cygnal (acutally Silicon Labs) web site.

Regards,
John.