built-in receiver phono preamps, how good are they

how good are the built-in phono preamps in the eighties receivers? i'm using the mc/mm phono input in my old denon dra-600 receiver for a phono preamp. denon dl-110 homc into the mm side, denon 300 and jvc dt-200e lomc's into the mc side with a jvc ql-y66f turntable. should i upgrade to something like an azur 640-p, would i hear that much of an improvement in sound quality? any opinions, comments, or advice would be greatly appreciated.
kindest regards, sam