For the AV Famicom set audio balance like this;
This will bring the AV Famicom very close to emulation audio balance, and all mappers will have great balance between themselves.
These settings also work with the AVS but the AVS expansion volume should be set to match one of the expansion games, then all other games will be balanced.
FDS: 50%
VRC6: 80%
VRC7: 100%
Namco-163: 50%
MMC5: 50%
Sunsoft-5B: 100%
As a side note, Digital Devil Story Megami Tensei II is the perfect game to test Namco-163, almost every sound is played with the expansion audio in this game.
KRIKzz's Namco-163 mapper sounds fantastic by the way.
Setting everything at 160% is a very bad idea, KRIKzz was very clear about the limited FPGA DAC headroom.
I have bought an Original Famicom (FF, VCCI, GPM-0x) and all the expansion audio cartridges (except Gimmick!), so I will report on correct balance and settings in two weeks or so.
I would really like to see KRIKzz fix the FDS modulation bug before releasing the final V20, it is almost perfect besides this bug.