Don’t know about replacement for the phone, but maybe a discreet player would work for you? Some old multibit Hifiman or a small but punchy Fiio could be fun and maybe even really cheap, depending on your location etc.

As for the headphones, did you consider Hifiman Sundara? It’s not an upgrade too expensive (relatively speaking ofc), and I heard they can be tailored well to one’s taste with eq, so maybe that could be an option.