I wonder if I would achieve further improvement in sound quality if I traded in the Luxman and bought a dedicated CD transport ( price range 3-4 K ).
No. Keep your Luxman as a transport til it dies. Take that money and buy an Innuos Zen Mk3 server/ streamer for about $2500. Load all your CDs directly into it and enjoy all your music from your chair in any order you wish. Plus, you’ll have access to worlds of music through streaming you would’ve never otherwise been exposed to. This, IMHO, has been the greatest upgrade in music I’ve ever made. I listen to my own music less than 50% of the time these days and have discovered so much more music that enriches my life so much more than any equipment upgrade ever has. Get the Innuos Zen and a Qobuz subscription and I promise you your audiophile experience will be totally transformed forever. Just my $0.02 FWIW.