Definitely get the second monitor! It has helped me immensely in communicating with my audience while streaming. It also lets me check, and thank people who are new / or up voting the stream as I can monitor this via either steemnow / steemdb / steemd / other tools that check the blockchain in real time.
Streaming is a lot of fun, with or without an audience!
Yeah, this is definitely the needed move if someone really wants to be a "professional" streamer. You just can't be a successful streamer without an additional screen.