We talking budget synergy or audiophile grade> <G>
Easiest test of how well things are working together is when you immediately feel that "something" is missing when you turn a component off.
** Another vote for having separate level controls for each component in the system. Amazing the difference a balanced line level start to finish can make, especially as the chain becomes more complex. Feeding the appropriate signal at each step brings it all together.
Oh. Speaking of complex signal chains ... my daily driver. Only took maybe 30 years to get everything optimal.