mhsmith What should be purchased first?
Speakers first pick the ones you like the sound of first in good Audio shops, as most shops will have them driven an amp that does them justice, as speakers can be hard or easy to drive.
Once you’ve got the speakers, come back here and ask which amp/s will drive them best, as some of here will look at the specs impedance/phase/loading etc graphs of the speakers you’ve purchased and recommend the right type of amp/s
Cheers George