You are on the right track. The AquaClear will not give you crystal clear, polished water "out of the box" because the sponge is not "graduated" and does not get out fine micron particles. To get crystal clear water, most people use tightly packed floss (Sera Wool is the best), usually in lieu of carbon. Seachem Purigen is generally considered the best chemical media. You probably have room for both Purigen & Chemi-Pure.
Also, Be aware of the bypass issues on the AquaClears:
AquaClear Bypass Issues
[I had to duct tape the holes on my AC50 get it to work properly.]