One caution. One of the most common, good quality choices is the Saunders 4 bladed 11"x14" easel. The adjustable part of that easel can be removed, leaving a fixed 14"x17" easel.
In some cases, people will confuse things by describing that easel as a 14"x17" easel.
The two bladed easels aren't as easy to work with for standard paper sizes (harder to repeatably achieve square, consistent borders) but they will take odd sizes of paper (like 12"x16") that aren't as easy to use in the 4 bladed versions. They are also slightly smaller in total size (for the same maximum paper size).
I have an 8"x10" 2 bladed easel, an 11"x14" 4 bladed Saunders easel and a 16"x20" 2 bladed easel - the Saunders easel gets used the most.