Please don't waste your money on hyper expensive cables or power conditioners ... etc. There are only two things that affects the soundstage depth:
Also be aware that some speakers do represent the soundstage depth more accurate than others. One example for exceptional soundstage is Sonus Faber Stradivari
- Recording (Production). Use Stereophile test CDs to test the SS depth. John Atkison have done great recording on this.
- Speaker placement - Experiment with the speakers by moving away from the wall behind them.
Also be aware that some speakers do represent the soundstage depth more accurate than others. One example for exceptional soundstage is Sonus Faber Stradivari