Such Great help before. Maybe some more help now

Looks like a great system.   Not sure about GR Research ....    I would trust your ears, if it sounds good, it's good.  Enjoy

The end game is always to enjoy your system. If you like it as-is, you’re good....but here you are asking! A system is always only as good as the weakest link, there’s always something that can be improved. It really depends on how far you want to go.

Upgrading your crossover parts could give you more refinement and clarity without a major change in their overall character, whether GR Research, Crite, or on your own with same values of higher quality parts. You could also damp the outside shell of the horns and inside of the cabinet.

You could also easily add an isolation platform to your SL1300G.

All are small steps in the direction of reducing vibration and resonance, and improving overall clarity.

Sounds like a really great setup. 

I don't think you can do much better, but many audiophiles get bored with "great" and start experimenting.   The tone controls on the Luxmans are really great, including the loudness feature, so I encourage you to experiment.

Also, room treatment is often something to consider, but your gear reads like a wonderful combination.

I’d be tempted to try a tube phono stage and listen to some Volti speakers just to see, but otherwise if you’re happy just sit back and enjoy.