The FTDI FT2232 might be worth considering as an alternative to the Cypress FX2LP. It's a lot cheaper and smaller, and might be fast enough:http://www.ftdichip.com/Products/EvaluationKits/FPGA.htm
The Silicon Laboratories CP2102 is also a reasonable candidate for an RS232 <-> USB interface.
<http://www.silabs.com/tgwWebApp/public/web_content/products/Microcontrollers/Interface/en/interface.htm>The advantage of the FX2 is that it is more than just an serial converter; it is a programmable 8051 microcontroller that can execute algorithms, such as programming the FPGA from a bitstream.
73, Lyle KK7P