Getting started with Headphone system; what are the basics

I have recently completed my speaker based system overhaul and am turning my attention to a headphone based system for my office.

I have little experience in this area and am curious about the basic amplification needed.  Also hoping to re-purpose a LTA Microzotl in this other system.

So here is the basic question.  Do HA based systems require both a pre-amp and a power amp?  I know the LTA HA products are integrated but I wonder if I could go with separates to find a new role for my MicroZotl.

Thanks for the help.