Hi, Ben, welcome to the forum.
The dual 8 projector of choice appears to be the Eumig Mark S810D. It will run super 8 or standard 8mm silent and sound films. You can usually pick one up in the $100 to $175 range. They have a 150 watt halogen lamp and a 600' take up reel capacity. This machine comes with 2 sets of sprockets and aperture pressure. These parts clip into the side door of the projector when not in use and are easily switched out to accommodate their gauges. Eumigs run quite and the sound is very good. There is also an aux out for external amplification.
Here is a review from our projector review category:
viewtopic.php?f=21&t=275if you find one on Ebay be sure to ask the seller if it has the sprockets and aperture plates for both gauges as they can get lost.