This is not a hierarchical approach, but a few tips.
First, choose speakers which image well (ProAc Tablette Reference, ProAc Response 1sc, Arcus Cello, Sonus Faber, Totem, etc.).
Experiment with positions in the middle of the room to avoid colorations from wall reflections. Do not place in front of angled walls; remove obstructions in back of the speakers to avoid wave diffraction.
Use extremely stable, heavy stands, that are coupled well to the floor, and raise the tweeter to ear level. Couple the speaker to the stand using either Blue-Tac, spikes, or Symposium rollerballs.
Take the crossovers out of the cabinet and place them on a dampened support at least a few feet from the speakers themselves.
Make sure the speaker cables are exactly the same length for each side.
(Although this is not really crucial for soundstage, you can experiment with different cable lengths for tweeter and woofer between the crossover and the drivers. The total signal length in the crossover is typically unequal for each. Also, decay times for tweeter are much faster than the woofer. If possible measure this with lab equipment.)
Bi-amp if possible with the same model amplifier. Hopefully the amp has a relatively short and uncomplicated signal. (SET amps, minimalist SS like 47 Labs Gaincard, etc.)
Use relatively simple speaker cables and raise them off the floor, making sure they make no contact with speaker cabinet. I prefer thin single-strand solid-core copper speaker cables directly soldered (with minimum amount of solder) onto the speaker terminals and crossovers.
Upgrade crossover components (capacitors, etc.). If possible, do away with all circuit boards for crossovers, and directly wire crossover components to each other.
Remove speakers and examine damping material in the cabinets, to make sure it is equal in volume and distribution. You can experiment with changing it, if you want.
Tighten the speakers to the cabinet.
First, choose speakers which image well (ProAc Tablette Reference, ProAc Response 1sc, Arcus Cello, Sonus Faber, Totem, etc.).
Experiment with positions in the middle of the room to avoid colorations from wall reflections. Do not place in front of angled walls; remove obstructions in back of the speakers to avoid wave diffraction.
Use extremely stable, heavy stands, that are coupled well to the floor, and raise the tweeter to ear level. Couple the speaker to the stand using either Blue-Tac, spikes, or Symposium rollerballs.
Take the crossovers out of the cabinet and place them on a dampened support at least a few feet from the speakers themselves.
Make sure the speaker cables are exactly the same length for each side.
(Although this is not really crucial for soundstage, you can experiment with different cable lengths for tweeter and woofer between the crossover and the drivers. The total signal length in the crossover is typically unequal for each. Also, decay times for tweeter are much faster than the woofer. If possible measure this with lab equipment.)
Bi-amp if possible with the same model amplifier. Hopefully the amp has a relatively short and uncomplicated signal. (SET amps, minimalist SS like 47 Labs Gaincard, etc.)
Use relatively simple speaker cables and raise them off the floor, making sure they make no contact with speaker cabinet. I prefer thin single-strand solid-core copper speaker cables directly soldered (with minimum amount of solder) onto the speaker terminals and crossovers.
Upgrade crossover components (capacitors, etc.). If possible, do away with all circuit boards for crossovers, and directly wire crossover components to each other.
Remove speakers and examine damping material in the cabinets, to make sure it is equal in volume and distribution. You can experiment with changing it, if you want.
Tighten the speakers to the cabinet.