upgrade from NAD S100 proprietary phono section?

I currently have a NAD S100 preamp with NAD's own Phono section and am curious what current piece(s) would constitute the first noticeable upgrade in SQ etc.

I like the current set-up but don't know how to judge it against newer equipment.

The NAD has MM/MC, 4 levels of gain, and several levels of MC loading
Seems to be discrete components, dual mono
Uses S100's huge internal power supply
DEAD QUIET, no RFI or hum in my system

Paired with SOTA Star-Saphire & DL110 cart