Best method to connect subwoofer to amp

I just finished a great post about my speakers and amp clipping sensitivity, impedance etc. highly educational, as I am a rookie in this hobby just starting out. One recommendation coming out of that discussion was to contact my manufacturers. I have a Jamo c 80 sub (1800 watts and with an adjustable crossover from 0 to 200hz) for two-channel stereo. the c80 has binding posts for speaker cable connections for spades and banana plugs. The c80 also has" Line in left/LFE and right.. My integrated amp is a Technic SU-G700 and its manual says to connect the sub to its pre-out left and right connections.
Listening to Paul McGowan ( PSAudio poobah) he says the best way is to run speaker cables from my amp to the speaker terminals on the JAMO which is my current practice. He says this ensures the same signal going to my main speakers (Canton 9k stand-mounted) and the sub are the same helping them disappear. As noted I am currently using that method and indeed my subs vanished.
However when speaking to JAMO the rep said the best way is to connect the amp and sub is through the Preout of the amp to the Line input Left /LFE and right of the sub, my Technic manual also says this.
There is no high pass filter involved in my system the integrated amp sends the full signal through the pre-out not confirmed by Technic but from what I’ve read. I mention this as my amp is only 70 watts and I would have loved to separate the bass to be driven exclusively by the sub so my main speakers could be relieved of that duty and as I understand it two benefits would occur 1 my stand-mounted Cantons would no longer have to play the bass and 2 more power would be available for the cantons.
It should be noted the canton9 k have two sets of speaker terminals on set for medium and high frequencies and another set for bass. I will not be buying a separate highpass filter at this time.

Given the above which is the best method (for musical benefits) to connect the sub or does it even matter which of the two options I use given my system?
Is one method safer to use than the other?
Am I missing anything I should be aware of?
Thank you for your help

It should be noted the canton 9k have two sets of speaker terminals one set for medium and high frequencies and another set for bass
That is for Bi-amp/Bi-wire, nothing to do with subwoofer connection.
Given the above which is the best method (for musical benefits) to connect the sub or does it even matter which of the two options I use given my system?
It is system dependent, my suggestion is try both way and let your ears decide, what sounded best is the best method.
If you can't hear any difference, I suggest go for line level connection, I think your integrated amp has the option of remote turn off the pre-out, which is good for late night listening.
Is one method safer to use than the other?
IMO, line level connection is safer, you have less chance to shorted the speaker cable.

Thank you you answer my questions perfectly much appreciated.

I agree with @imhififan on this. People hold strong opinions on which way is better, but the diversity of opinion itself shows it's system- and listener-dependent.
A general rule with hifi is that you don't want to amplify then attenuate or attenuate then amplify. In an ideal world you amplify once (to the level you want to listen to) with no attenuation (volume control). This is not practical but an ideal situation.
If you use the speaker cable inputs on the sub your power amp amplifies the signal enough to run speakers, then your sub will need to attenuate this back down to line level before doing its own amplification. If you use the line inputs then it only gets amplified once i.e. better, with less distortion and noise.
The only problem may be if the coax picks up noise, if it does it will be obvious.
The best way by far is with wire.
Pragmasi  off this topic you mention "attenuating" the signal. Which rases another question I have   The Technic has an attenuation option of 20 db on its volume control. If attenuation is OFF the volume control reaches clipping levels at about 1/2 a full turn, if the attenuation function is ON   the volume control can be used to a full turn before hitting clipping levels. I keep it on so I can have more control over the volume level.
 Do you or anyone else reading this know if attenuation at the volume control level has a negative effect on detail, soundstage, imaging. I would not think so but what do I know.  
You can't have ideal world if your source is digital!
I'm in agreement with imhififan as well.

I've tried it both ways in my system..... line level won out. Some subs are specifically designed to work with speaker level connection like REL.
Scott, I know you said " I will not be buying a separate high pass filter at this time." But, I am a notorious PITA and have been using subs since 1976 in every conceivable configuration always trying to match them to one type of planar dipole or another. You can not attain the full benefit of subwoofers without an adjustable 2 way crossover that has a  speaker delay function. Room control is a useful additional benefit.
Sometimes the best solution is just not attainable usually for financial reasons. This is always the case for me. This makes our systems evolutionary which is fun and we get to appreciate each additional improvement to the fullest extent. I always know what the next evolution is way ahead of time.
I find that people tend to use shortcut solutions in audio thinking that somehow they will come up with the ultimate solution (without spending a lot of money) I certainly have been guilty of this. But, relative to a dedicate subwoofer management system the other alternatives are seriously inferior. Certainly you may need to use one for the time being. But, know that if you are looking for the highest performance you will need to make the jump at some point by either getting a separate cross over like this
Or switching to a preamp that has this function like this 
Thank you for the advice and your time I will save this information. I'm one of those vanishing middle-class retired guys. I used the pandemic relief $$ , sold my existing system from 1980 and some camera gear to buy newer gear, from local sellers on Audiogon. I wanted to give stand speakers a shot as wife was not fond of the big Snells(sad to sell them). 
I must admit the new system just blows away my old gear in all respects except volume which is still fine it is plenty loud the Jamo c80 came with the Cantons( love their sound) and are just OK as filler in my compromised(read married) listening room. Chairs go here, sofa there, plants up there, the coffee table... I have moved that out for a clear line of sight to the  speakers.
 I digress to the point I have to save $$ and was looking to buy a Node 2i next, next year.
Who knows what will happen in these dark times as the second wave is creeping back to the northeast. be safe stay well. 

Nice information will check in to them some look affordable. My goal is to stop the low bass from playing on my stand-mounted speakers so they can concentrate their efforts on the mid bass on up.
My goal is to stop the low bass from playing on my stand-mounted speakers so they can concentrate their efforts on the mid bass on up.
If that’s your goal, a high pass filter is a must!
Since your integrated amp not possible to insert a line level high pass filter, your only option is to insert a pair of speaker level high pass filter between the speaker and integrated amp speaker output.

SU-G700 speaker output --> speaker level high pass filter --> Canton 9K

You can find some inexpensive speaker level high pass filter at Parts-express for experiment:

For best result, I suggest Bi-wire configuration:
Disconnect the jumper bars from the Canton 9K speaker terminal,
connect the speaker level high pass filter input to integrated amp speaker terminals, output to Canton 9K low frequency terminals,
connect the Canton 9K high frequency terminals direct to integrated amp speaker terminals, so the high frequencies will not go through the speaker level high pass filter.

If you like the result of this setup, you can upgrade the capacitor in the speaker level high pass filter to Film Cap to further improve sound.
Thanks for the advice! I will definitely look into this. I appreciate your time.
IME, I always found that a good high pass filter greatly improve dynamic and clarity on small 2 way monitors.
If you’re going with Paul McGowen’s approach, I think the best way to do it is to grab the signal off the speaker amplifier binding posts, drop the voltage drop, and send it through a DSP and then to the subs. This lets you shape the bass waves which is an audiophile requirement for low bass in small listening rooms.

You may also find that high passing the mains increases overall sound quality, especially at higher output levels.
Scott, I am also in the Northeast. If you are over 65 just keep your distance from others. Skip the concerts and those late nights at the bar for now. This is all going to blow over. I think the main attraction here is they way this is permanently going to change the way we live. People who never shopped online are now addicted to it. Malls are going to converted to nursing homes, retailers are disappearing. People working from home are more productive! Sure, if you done have to waste 3 hours a day in the car. Downtown real estate is plummeting in value. Who needs a big expensive office. 
Anyway, sad to hear you sold your Snells. Those were great speakers.
If you want to increase your output get a crossover like the JL Audio unit and a second subwoofer. This will allow you to raise the crossover point without harming the image as long as you place the subs correctly. I cross over at 125Hz. It is easier to match subs with a higher crossover frequency because the wavelengths are shorter. The low crossover points that you see being used work better with one way crossovers and single subwoofers. It adds low bass but does nothing else for the system. Using a 2 way crossover, two subs (or more) and a higher crossover point reduces distortion in the main speakers, increases headroom and gives you much more flexibility in adjusting the bass to your preference. 
You crossover at 125? Does that limit the placement of the subs to right next to the mains?
you explain the best method to connect the subwoofer to the amp. This is a helpful discussion of the day, yet. I am also a researcher if you have any technical problems so you can get a solution with us. I found the solution to the error 101 chrome problem. you can read if you don't know about it.