Well in fact bauds correspond to the frequency of the carrier, if you code one bit for each period, then yes bauds and bps are equal, but if you code 2 bits per period, bauds are half the bps and so on.
One could use the ftdi chips (FT232BM for example or the DLP-USB232M module ready to use), they come with windows and linux drivers and support 300bps -> 3Mbps in TTL (the base rate can be divided by numbers between 2 and 16384, so 62500 is an exact match).