Actually, they did come with the AT3600/L. We have taken in at least three dozen PL-600's and they all had that mounted. The only exception was when the headshell wasn't original.
We have these available - brand-spanking new: https://www.ebay.com/itm/143958231265
They are slightly different than the original Luxman hinges but will work just fine.
For me the number 1 would be the Carver Amazing Loudspeakers (found in a thrift store for $75!) followed by the Yamaha NS-1000M's and lastly, after many years of listening, I'm still enjoying the ADS L780/2's in use in my office.
Not sure if you did this or not, but for this to be an equal comparison you would need to be listening to a Spotify Premium account through a DAC into your system. Both (Premium and a decent DAC) make a profound difference - the single greatest improvement in sound that I've noticed through...