Cimpliance Vs Cartridge loading

Hello allI know I'm a pain, but need help??I have a PS Audio, phono stage, trouble is cartridge, loading starts at 100 ohm, then next adjustment, is 500 ohms, I'm running a Dennon?Zu 103, rated as 300 ohms, into 500 ohm, Yea great bass, but the treble is far to harsh, turning, back to 100"ohms,  I have lost all my bass slam??, an the sound is very boring!!, I'm stuck!!
I'm thinking of buying the "Herron VTPH 2 A phono stage, I don't know how this will sound, or is available in Australia??, at lease I can insert any RCA connectors?? , But am confused the difference between  impedance, and cartridge loading??, can some one help, with all the above, the main object, is to keep the great bass, but shaved the top end, just a bit??, it is a bit hard for me as you have many shops, in the US, we have three, and where I live, I'm four hours drive, from them, but they are not any where good??, cheap stuff!!,
Regards
David SpryAustralia