Generally as simple as possible, but not simpler. Not using a preamp typically significantly reduces the sound quality. Typically separate preamp and amps sound better than integrated… but you have to be carefull how you compare.
Two box preamps, monoblocks amps sound better than stereo amps. But adding non-essential functions and boxes is not better.
Overall “straight wire” systems, with the shortest possible path and least functions (no tone controls, no extra manipulation) sound best.