Power cords or power conditioner

I agree with most here that speaker placement and room treatments is the place to start. You need to get that right first.  The biggest thing that made an impact to soundstage depth for me is having the speakers towed out, so that they are almost firing straight ahead.  But that applies to my B&W 802’s, it might be different for you.  Definitely suggest playing with toeing out your speakers though, in addition to the other suggestions regarding speaker placement.

After that, for sure, I find power cables (and other cabling) and conditioners all play into the degree of soundstage depth as well.   However I found that the few conditioners I tried altered the tonal balance adversely.  I found that the Torus RM20 (which is not a conditioner but rather a big honking isolation transformer that weighs 90 pounds - super simple and super effective) was far more even handed and has more instantaneous current supply than your amp could ever want.  Torus told me that moving up to the more expensive AVR20 is pointless provided your AC supply stays within 4V of 120VAC.  They suggested I purchase a Kill-A-Watt meter from Amazon, which I did, and I found my voltage to be fine.  So I stuck with the RM20.  

After testing my amp (Gryphon Diablo 300 integrated) connected to the Torus and to the wall, I found it was actually best through the Torus.  This was NOT the case with the Audioquest Niagara 5000 I demoed where my amp sounded unquestionably better connected directly to the wall.

One clarification - when I mentioned that the Torus is not a conditioner, I meant not in the traditional sense. Rather than filtering noise out, it electrically isolates your system from your house’s AC.

Interestingly, it was Nordost who first turned me on to Torus, when I had some questions about my Valhalla 2 speaker cables. They told me they thought conditioners can be tricky and unpredictable and yes, they also mentioned they can have an effect on tonal balance. They then suggested I look into Torus, along with another industry-veteran contact of mine who also strongly suggested Torus.

The RM20 definitely helps with soundstage depth. Details become more coherent, and I find that mid and upper detail are prerequisites for soundstage depth. Or maybe they just happen to always go together, not sure. But as mentioned speaker position and room treatment first…

And, dare I say it given the controversy in my other thread regarding power cord length: I think @ghdprentice found that when comparing like power cords of differing lengths, the longer cord offered a deeper soundstage? His test was with Audioquest Hurricanes.  And while I think of it - in my experience if you are using a USB cord shorter than 1.5m that will also clobber your soundstage depth somewhat and will compress everything more.  I did this test with two Audioquest  Diamond USB cords and two Nordost Valhalla 2 USB cords.  The longer cords from both manufacturers were blatantly better than the shorter cords in terms of openness, detail and soundstage depth.  I thought it might be a burn in issue at first so I actually ran the cords hundreds of hours, with no change - longer cords were superior.  So you might want to ensure you have no ultra short USB cables.  

in the words of Nelson Pass the power cables supplied with Pass amplifiers are sufficient to deliver more current than the amplifier is capable of.  Typical of most reputable amplifiers.  

Bark up another tree to improve the sound in the ways you are attempting.  

@nyev  My usb cable is pretty short, I'll have to look at it but I think it is around a meter.  I've also heard that a longer power cord will work better than short one.   Never experimented with it thought.   

As to speaker toe in, KEF states in their owners manual for the KEF Reference to not toe the speaker in much.  They claim that their speaker design doesn't need toe in like many other speakers.  I've played extensively with this over the 2 years I've had these speakers and I agree.  When I used Monitor Audio speakers they responded well with pointing the speakers at ones shoulders as someone suggested. 

While I'm new to a dedicated 2 channel set up, I've had many very high end HT processors over the years.  Lyngdorf MP-50, Lydgdorf MP-60 2.1, and now a Datasat LS-10.  I've also had some very nice amps including 3 BHK 300's that ran my front speakers.  The issue that I kept running into with the amps is nothing really sounded better than my current ATI amps.  A Mcintosh MC207 was the worst amp I've ever had in my system.   Now with the Luxman, I am seeing a nice improvement with things.

I did order a Shunyata Triton V3 with an Alpha HC PC.  I should have that possibly tomorrow.  It was between the Shunyata and the Torus I'm going to also order some sound panels to take care of the first reflection point.   I live in the City of Chicago, so I have a hard time believing my power supply is clean.  We will see, if the Triton doesn't do anything for me, I'll sell it.  

Meh. What does Nelson Pass know?