The flip side of synergy as it is applied to an audio system, is that the end result is subjective, which is not measurable. When components are put together in such a way, which either compensate or compliment the shortcomings of the components themselves, you can still wind up with something that might sound good to you, but it's a bit of a house of cards. So if you swap out a piece of that system with a component that would normally be remarkable, the whole thing collapses. It doesn't mean that you can't make improvements, but it can make it difficult to appreciate the merits of components that are typically better performers.
On the more nuts and bolts side, there are things like Joe was talking about. The right material mix in caps will alter the properties and thus measurable. Same thing on carts and arms. You could go pick out the best MC you can afford being led that MC is the best choice only to find that the right MM for the arm you HAVE would have worked better. This is when things can go really bad on advice. If you had an inferior match to begin with, and you don't change the table and arm, and people are telling you to flip all the rest of the gear all the way up the chain, the potential might eventually rebalance the rest of the system but off a poor performer. So by the time you get to the right TT/arm, you'll end up with something that sounds like shit all over again.
On the more nuts and bolts side, there are things like Joe was talking about. The right material mix in caps will alter the properties and thus measurable. Same thing on carts and arms. You could go pick out the best MC you can afford being led that MC is the best choice only to find that the right MM for the arm you HAVE would have worked better. This is when things can go really bad on advice. If you had an inferior match to begin with, and you don't change the table and arm, and people are telling you to flip all the rest of the gear all the way up the chain, the potential might eventually rebalance the rest of the system but off a poor performer. So by the time you get to the right TT/arm, you'll end up with something that sounds like shit all over again.