I don't know much about c8051f320, but I have personally use Cypress's 68013A chip. And this I can tell you, it is a great chip to work with. While the USB assembly learning curve is kind of big, but it was well worth the time. I really like the GPIF interface AND the concept of software enumeration is simply amazing. Driver is good and the examples are well done. Personally, from what I have heard from other ppl the cypress usb chip is one of the best High Speed usb chip out there.