Thanks to all who made suggestions regarding this problem. I have purchased two Elgato Video Capture devices and have been using them quite successfully. We've run nearly 40 hours of VHS, 8mm and Digital8 through both devices and the results have been quite good. The Elgato software is primitive but effective, allowing for some control of the image as it is being captured. Both RCA and S-VHS inputs perform as expected and the audio is fine as well.

Our source decks are two Panasonic AG-1980s (VHS) and two Sony EV-S5000s (Hi-8)