Buzz, you got lots of options. Just about any Matrix, 100 series, 300 series, 500 series, 700 series or 900 series unit will work off the Minn Kota Universal 2 transducer. Stay away from the 3D units but all the others should work. Since you have the US2 I would at least get a 200/83kHz DualBeam unit. You did not say if you want a Sonar-GPS Combo "Chartplotter" type unit (has maps, can use map cards, could be an NVB version, has the Mark, Goto, Info and Zoom buttons) or a Sonar "Trackplotter" type unit (will not display maps, no sonar or image recording as there is no SD card slot, all GPS functions are performed through menus and not with committed buttons as in the Chartplotter type units).
Got a price range or screen size/resolution in mind?
How do you plan on sharing the GPS receiver (there are 3 options that I know of)?
Do you want to be able to share waypoints between units while on the boat (you would need the InterLink for this).
Greg Walters at Humminbird