Good Evening, Brian,
16 x 20 trays require about twice the chemical volume compared to 11 x 14 trays. If you intend to process only a couple of prints, the required amount isn't too great--just enough to give good coverage to the paper. If you intend to make a number of prints in one session, it's good to ample quantities of chemicals, just so that chemical exhaustion doesn't occur toward the end of a printing session.
Another very viable option, especially if your working space is limited, is a drum originally made for color prints. Chemical quantities are quite small, but a motor base for rotation is, while not an absolute requirement, highly desirable.
Washing with a tray siphon is quite practical if you use RC paper. A 20 x 24 inch tray is preferable.
Handling the larger paper requires a little practice, but it's not really difficult. Allow plenty of time for chemicals to drain off the print before transfering from one tray to the next.