Do you use a Subwoofer when listening to stereo?

it is not fine to run satellites full range while adding subs for three reasons. First is you miss the opportunity to lower distortion and increase head room significantly in the satellites. Second is you make integration much more difficult. You are down where the wavelengths are over 10 feet up to 30 feet. Unless you are using digital bass management matching phase and time are difficult, usually by trial and error moving the speakers and perhaps by using a phase control on the sub. Without a two way crossover there will be more overlap making the problem worse.

I get the part about distortion and headroom in the mains (which you are calling 'satellites'). Its an issue that has concerned me. But as far as getting matching time and phase, below 80Hz its simply not a thing. The reason why has been explained here several times so I'm not going to repeat it.

I ordered a pair of the Swarm subs to supplement my Classic Audio Loudspeakers which are flat to 20 Hz. The problem is I have a standing wave at the listening chair and too much bass elsewhere. So I only need two subs and I got Swarms since they are designed to operate inside the room boundary effect. I need them to be against the walls out of the way. Here are the instructions Duke sent along. When you look at his comments, its obvious that all the things that you are commenting about are on his mind as well, but are easily solved without resorting to DSP:

You MIGHT try this: Start the subwoofer amp's phase control at 90 degrees (that may change later in the process), and wire the two subs
in opposite polarity from one another. This will tend to prevent them from making the low bass region too loud, while they are improving
the in-room bass smoothness. If the two Swarm subs are to the left and right of the listening area, this may also increase the sense of
immersion in a large acoustic space.

I normally leave the 18 Hz protective highpass filter ON, but that's up to you. Also, have the "Bass Boost" off. These controls are
on the back of the amp.

As a suggested starting point, going from left to right across the front of the subwoofer amp,
first the EQ: Frequency 18; Bandwidth .1; Level "0". This effectively turns the EQ "off", so it's in reserve in case we need it.

Next the other controls: Phase 90 degrees; Frequency 10:00 (about 75 Hz); and Gain at 11:00.

If you are going to be "dialing in" the subs by ear, here is the sequence of events that I suggest (you can also use this sequence
if you're using measurements):

1. First, adjust the Gain for best sound. This is the control which will make the most difference.

2. Next, adjust the Frequency. This will make the next most difference.

3. Cycle back through Gain and Frequency at least once.

4. Adjust the Phase. This will make the least amount of difference.

5. If there is too much bottom end, try plugging one port, and then unplug that one and try plugging the other.
If it's still too much, plug 'em both.

6. If there is not enough at the bottom end, try putting both subs back in "normal" polarity. If you lose smoothness from doing
this, go back to having one in reversed polarity and plan on using the single band of parametric EQ.

7. If there is still a problem area, OR if you need to boost the very bottom end, use the parametric EQ. Unless you have
measurements, expect some trial-and-error.

8. Cycle back through Gain - Frequency - Phase one last time.

It may still take several days before the Gain is dialed in exactly right. There are two reasons for this. First, the ear is
especially sensitive to changes in SPL in the bass region, so a small change makes a larger perceptual difference than you would
have expected. Second, the little knobs on that Dayton Audio amplifier are maddeningly small, so it's real easy to move the knob
more than you intended.

Having had some exposure to only marginally integrated subs, leaves me to keep my wishes clear of any subs rocking my guts. (I'm not into 'thunder and lighting' AV shows either.) So, 'Horses for courses' I'd say.

@justmetoo — I’d say you’d do well to go hear a system with well integrated subs as you’re completely missing (and mis-categorizing) the benefits they can provide.  And subs could also actually help alleviate the slight bass overload issue you’re experiencing.  Keep an open mind on this and you might be rewarded greatly. 

It is all a personal taste.  Some do like it, some do not.  I do.

@ozzy62 --

...
If your speakers are generally of the full range variety, no need to add an additional electronic crossover to the mix. KISS applies here, less electronic artifacts, the better.

It depends on the specific set-up and quality of the digital cross-over (which needn’t be expensive per se); where well-chosen it can, potentially, lead to an even better outcome with the main speakers high-passed. For this to have the best effect (i.e.: a HP on the mains) it seems generally accepted that a cross-over no lower than ~80Hz leads to the best outcome in taking advantage of relieving the mains (+ their amp(s)) from the central to lower bass, leading to 6-10dB more headroom and a likely cleaner, more effortless reproduction (with 2-way main speakers the benefits of a HP may be even more pronounced as this more obviously affects midrange cleanliness).

Such an approach however may call for added attention in regards to subs placement being in symmetry with the mains, as directivity will have a bigger say with a chosen, higher XO-frequency. Theory may dictate it’s difficult to nigh on impossible to localize bass even with a XO up to 100Hz or a bit higher to the mains, but when practically experimented with I’ve found placing a pair of subs symmetrical to the mains is very beneficial, even when crossed into the 70’s.

This type of set-up with two symmetrically placed subs would still be compatible as a future DBA, as additional subs could be crossed lower and placed more freely to best take advantage of smoothing out room modes, or where ever interior decoration may dictate them to be placed. In fact that’s what I may intend at a future point, adding to my existing two subs.

For all its apparent prowess a DBA set-up as configured with the mains run full-range doesn’t take advantage of the potential gains to be had with a HP on the mains and a higher XO here. Added component complexity in the form of a quality digital XO - while justified, to my ears, run in the signal chain over passive speakers - mayn’t be so in every case; my set-up is fully active via separate components, and as such the digital cross-over used is, by necessity, in the signal chain to begin with acting as the XO (without ANY passive filter components) for both the mains and subs, and so a high-pass on the mains isn’t adding more physical components, but simply an extra high-pass digitally.

Atmasphere, phase is only half the issue time is the other one. I find it rather comical that people can say phase is not an issue. Wire one of your speakers 180 degrees out of phase and what happens to the bass. Any fundamental from impulsive bass sounds such as bass drums disappears. Most people would not notice this because their systems do not produce these fundamentals in the first place and I think this is what most of the mythology stems from.
Now it is true that the wavelengths are very long and physically getting a subwoofer 180 degrees out of phase would mean backing it up 15 feet and the degree of out of phaseness depends on the frequency. But, if you do that you have now created a 15 msec delay between arrival times making the situation even worse. Accurate bass transients at the listening position at least, requires the arrival times of the sound from each speaker to be exactly the same with the signal being in phase. In order to do this you need to be able to measure what is going on and then make the appropriate adjustments. In my case the computer makes the adjustments for me. I also have the ability to manually change delays and phase so I can demonstrate to you exactly what happens to bass transients. These are not something that you just hear by the way. They are something that you also feel. Now, I use four subwoofers but they are arranged in a specific way for a reason. They produce a single wave front without interference from the side walls floor or ceiling. There is essentially no back wall because of the way I designed the room. That wave front gets to my recliner at exactly the same time and in perfect phase at all frequencies as that of the satellites or main speakers. 
Swarm systems where you are placing the subwoofers at various random points in the room is a way of dealing with your typical room acoustics.
It is not necessarily the best way to integrate subwoofers with your main loudspeakers. Whether or not you can actually make it work satisfactorily? I have no idea. I have not measured a system set up that way. 

Nobil100, it is not just what you hear, it is what you feel. Eventually you will get a proper crossover and learn. Unfortunately, accurate bass below 40 Hz is a rarity is home systems. In order to use subwoofers at the state of the art you need digital bass management. Without it you are lost. If you think you can get it right just by listening...just keep listening. Listen to live performances in smaller venues like jazz clubs. See an artist like Dave Holland then buy one of his records. Are you even close?

 Adding subwoofers under the main speakers is just a cheap easy way to do it. The manufacturers would not be able to sell subwoofers otherwise. The Swarm system is a great way to deal with room acoustics which do cause a large share of the problems related to bass reproduction but not all of them.