Rated reliable robust android

Recommended Sony android phone to run latest version of ntrac.
I have a brilliant old Xperia zx1 Compact - totally reliable and ridiculous value given how long its running, but it struggles running e.g piano synth. What do I need to get to combine running ntrac to a high standard and a compact phone that good? Boring question, but I’m cutting to the chase…
Budget: £100 - 400. Ish!
Answers greatfully appreciated.