I have only read the OP's post and will comment on their inquiry.
As an example there is a Speaker Designer Troels Graveson (TG), who offers the Schematics/ Parts/ Cabinet Dimensions using a selection of Brands products for his own Speaker Designs.
The general consensus in the community that uses these designs, is that a Basic Speaker Design, that can cost between $3000-$7000 to produce if done correctly as a DIY Build, can easily compete in the arena with Commercial Products costing 6x - 10x the Build cost of a TG Design.
In many cases TG offers a Xover Upgrade for these designs, that can add another $500+ to the above build cost. It does seem the utilisation of the Upgrade, produces a coherence in the SQ and gathers the presentation to where it can be perceived as more honest and believable. It does not necessarily mean the measurements produced for the Speaker or the Speakers impact on Room Modes are going to change.
Note: All that is produced Upstream of the Speaker Xover is Signal not Sound. All that is produced downstream of the Xover is Sound, and it is the perceived quality of the Sound being produced that has the attraction/detraction element, during a system in use evaluation.
My advisory to an individual with the confidence in their skills and wanting to attempt to attain a improvement to the SQ produced from a Speaker by swapping out Xover components is to work with the Internal Wiring as the initial investigation. Changing Internal Wires can have an impact on the perceived SQ that impresses. It is also one of the most cost effective measures to utilise to increase the experience of what can be attained. When a Internal Cabinet Wire is discovered that meets with ones attraction, this can also be considered for use externally as a Speaker Wire, the unknown is how the Connections at Amp' and Cabinet can have, as a detrimental effect can occur, leaving anticipated expectations not quite met.
If one is really bold, not too concerned for the convenience of using connectors and are in possession of End Game Amps and Speakers that are out of a Warranty period. There is the Option to Wire from the Amp's Internal to the Xover bypassing connectors. As a option it is easily undoable and returned to the original build method.
It does not take long when using the Web Sites that have assessed numerous Cap's for their influence on a sound, that when the most rated ones are costed for , there is a outlay fast approaching a $1000+. That becomes a lot of money and burn in hours to learn if such a change to the Xover has been valuable for the SQ.