> 1 - Get an amplifier that has a "Night Mode" function
Well, or get a compressor/limiter that you can jank into any signal chain, so you don't have to buy a whole new amplifier. You can find cheap compressors/limiters for like under $100 I'm sure.
This would be a good option provided the source is stereo and either the speakers are active or the amplifier has a processor loop.