On the Aventon website, the frame stack for the 57cm frame is 35mm higher than the 55cm frame, with 9mm longer reach than the 55 frame (MATARO LOW ? Aventón Bikes). So it would seem the 57 will have a taller front end relative to your saddle height (the 57 has a slightly steeper seat tube, but I would think you could neutralize that by fore-aft adjustment of the saddle).

That said, it is impossible for me to know how the 55cm or the 57cm will compare to your current bike.