Two fives and Two subs on Stereo mode

The OP is a little off.  The 2 Subs in a home theater configuration are not "stereo".  They both play the same ".1" signal, there are no "stereo" subwoofer signals in 5.1 or Atmos audio.  Indeed, with a proper subwoofer, there is no concept of stereo at the Sub level, because subwoofer frequencies are hard to localise, meaning the ear doesn't know where it is coming from, making a stereo signal from subwoofers rather useless.  You might as well just turn up the sub you have.  So the statement "I am a music enthusiast and prefer to listen to music in stereo mode" when talking about subwoofers, like many so called "audiophile" statements, is rife with inconsistencies.

Was just about to place an order for two fives and two subs when I saw this. Have this bees sorted or should I settle with just one sub?

Two Subs in a stereo set up still is not possible.

You might find that stereo Subs isn’t going to be an improvement as the low frequencies are very non-directional.

If it was a big selling point you’d see someone selling stereo sub-woofers and stereo sub channel AVRs. They may be out there but I haven’t seen any and I sure haven’t seen any media with a stereo sub tracks.

In the horizontal orientation a single FIVE is stereo, but one must be very close to the speaker in order to realize any practical stereo separation. If you break up the stereo paired FIVE’s into individual speakers, you can attach a SUB to each FIVE, but there will never be a full “left” or “right” FIVE in a Group. You could create a sort of faux stereo system by shifting the balance control on each FIVE in the Group. You’ll need to experiment with vertical and horizontal orientation in order to decide which is “”best”.

This is a “be careful what you wish for” trap for the unwary. In addition to the point above, two subs can even interfere with each other, leaving the outcome of two to be worse than that from one. And as far as room filling presence is concerned, one Sub can do the job in any space where two 5 suffice. Indeed, the 5 pair+ Sub set up usually needs Trueplay tuning to deliver some necessary control over the Sub to avoid bloated bass lines. Using two Subs needs someone that knows what they are doing to get a good outcome and this involves careful placement of both units. I also suspect that the Trueplay trick of overcoming poor speaker placement will not be easy to do where two Subs are placed in acoustically poor locations.

The above well known advice is the reason to hesitate before adding a second Sub in the same space. Another way to do the same thing suggested is to place the Sub where you will be listening to the set up and then do the wall crawl at floor level, along all walls, to see where the Sub sounds the most punchy and then locate the Sub at the point alongside the wall. Doing this for placing two Subs can be tricky and almost certainly not worth the bother, given that low frequencies cannot be traced to where they come from and therefore do nothing to enhance the stereo illusion.

While a blindfolded observer’s accuracy is low when asked to point at the subwoofer, accuracy improves when the subwoofer is placed too far from the main speaker. For example, for L/R in the front and subwoofer in a rear corner does not sound right for many listeners. But, I know one person who loves this arrangement because this person is a bass freak and in this room the subwoofer location offers maximum bass. To me the result is very poorly equalized and spatially disjointed. Fortunately, I don’t live or spend time there.

The best subwoofer placement is vaguely in the plain of the speaker(s) it supports. Off to one side or under a nearby coffee table will be satisfactory.

@buzz  No argument there, especially for music play where integration of all speakers becomes important. I would never place a Sub for music in a corner opposite to where the main speakers are in a music play set up, even if that corner was the best for the Sub, for precisely this reason.

I have found that the best placement for a Sub is in the plane of the speakers, anywhere between the two main speakers, as close to the centre as practical. And then, in the case of Sonos, let Trueplay optimise things. 

The opposite corner may perhaps work well for movies where the referred integration is less important than physically feeling the effects.

PS: for completeness for those interested. The can’t locate the sound starts applying as frequencies drop below 80Hz, or even 60Hz. Frequencies from 80-120 Hz, and all above that of course, can be located to where they come from and in much acoustic music, much of what are low frequencies are such locatable ones. Hence all of the above.

My current setup, forced by the room, is an Arc sitting about four feet out from a corner on a TV cabinet. Behind the cabinet and directly in the corner is my Sub. The main listening chairs directly face the Arc. Behind the chairs in the opposite corner from the Arc and Sub I have my two surrounds. All far from optimum but very listenable.

Due to the open nature of the room I could well use a second Sub, likely placed between the Surrounds in that back corner but spousal push-back says not any time soon.

I spent a lot of time playing with Sub placement with my old Denon - Infinity AVR setup and that front corner was the sweet spot according to both my ears and the Infinity setup toolkit.