I had totally missed this utility from Rogue Amoeba, but I'm using it daily now. It replaces the Volume control in your menu bar with a panel that allows easy individual control of devices/volumes for Input, Output, and Sound Effects. It also has a Play-Thru feature that lets you easily monitor any input source from any output source. Lastly, if you own any other Rogue Amoeba product (Airfoil, Audio Hijack, Fission, etc.) you get a [complimentary license](https://rogueamoeba.com/store/deals/ComplimentarySoundSource.php).