Throwing a digital to analog conversion into this seems like a lot of extra work to me since you already have digital data.

You may need to add a few buffers, but you should be able to directly drive the displays from your favorite PIO's (programmable I/O port) on your favorite µP. I'd probably use a Raspberry PI, because it is inexpensive and there is a large, enthusiastic support network. An RS232 port for the Raspberry PI only costs a few dollars. A USB port is built-in. If you are more familiar with PIC, go with that.