Basement Wiring

I am remodeling my basement replacing old ceiling with drywall. It had 3 light's run off of old type wiring, dropped in center of basement rafters, then it was wrapped & taped to the 3 lights. It is controlled by switch on top of staircase. I am putting 6 new Halo's in with new wiring on its own circuit from the main panel. I want to put a 7th Halo at the bottom of the stairs using the old wiring controlled by the stair switch. Do I put the old wires in a junction box tied to new wires going to the 1 Halo? If so do I need to have a small opening access door in the drywall ceiling for the concealed box. Is there any other way of doing this with out the access door in the ceiling? In my new wiring in the rafters from Halo to Halo lighting can I use NM-B Romex, or do I need to use Metal Clad or Armored cable? Thanks, Ed Bay Village,Ohio.