TeamViewer seems perfect for your company! The software company I work for also uses it. I guess as soon as you're using it in a company you have to buy a license, though it's generally free for private use.
It is not only available for Windows but also for Mac, Linux and even all kinds of Mobiles (no experience with that).
You can set to only share your screen but can also let someone (or everyone, if in a meeting) take control of your computer. It also lets you reverse the connection live so you become the one viewing a screen and the viewer becomes the broadcaster or vice versa.
I can confirm, that TeamViewer neatly works with two screens. Since the menu says "Show all screens" I suppose it also works fine with three or more screens.
We use this very often in our company. I also once participated in a meeting, where all developers viewed the screen of the instructor. I have not once had problems with the software. In the beginning you just have to get used to the menu options and figure out how you can set it up perfectly for your best personal experience.
I have not used the voice sharing option yet, but as the rest works well, I think also voice sharing will.
We used another software when I joined the company but TeamViewer is by far the best I know!