There is one COMM port header on the motherboard and you can plug in that header that you linked without issue.
Avoid the USB to RS232 adapters at all cost. USB is only rated at 5v while RS232 is standard +/- 3 to 15 volts but tolerant up to 25 volts. Such converters have a tendency to die out and may damage the USB controller.
I'll probably be adding the same thing to my 77 motherboard soon, please let us know how the connector works out.
BTW, I've been using USB to serial RS232 and RS485 for years, a lot of the cheap converters are indeed junk, but there are quality vendors. Try B&B Electronics, they also have great free help files for serial communication.