It appears that the LOMC phono stage of your Luxman L-505u integrated amplifier presents a non-adjustable load impedance of 100 ohms. The Benz cartridge is specified with a recommended load impedance of 400 ohms to 47K, and therefore appears to not be a good match. Not sure about the other LOMC's that have been mentioned, but compatibility with 100 ohm loading is a factor that should be considered for any LOMC candidates.
Regards,
-- Al
Regards,
-- Al