Connecting a sub which way to go

WRONG!

This underscores the MISINFORMATION that is often perpetuated on these threads. Paul McGowan DID NOT SAY TO RUN HIGH LEVEL FROM SPEAKER OUTS!

To directly quote Paul: "You want to let your main speakers go down as far as they can naturally. Don’t roll them off. The subwoofer should fill in whatever is missing in the main speaker."

You want to use line outs (optimally left and right line outs to two subs) of your preamp to your subs so that you can integrate them while utilizing the FULL RANGE of your mains.

The beauty of SVS subs is that they have a continuously adjustable crossover that you can fine tune so that they pick up where your mains leave off, maximizing integration. This way you are not constrained by the standard 80 Hz crossover typically used on a speaker level input on the sub, e.g., Velodyne. 

Please watch: https://www.psaudio.com/askpaul/why-dont-your-products-feature-a-subwoofer-output/

Wow chill out. What makes Paul McGowan such a god I wonder.
Some sub mfrs like REL recommend high level, I would trust them as one of the best sbwfr makers.
OP, whatever sounds right to you is best.

This is about the wilfull spreading of inaccurate information, not about Paul McGowan as an expert. REL doesn’t control the subwoofer market. I’ve tried their products and was unimpressed.

I have tried it both ways. As I see it, running the sub from the preamp out while running the mains full range is the way to go. Why? Just think about this ... the internal crossover in a sub probably uses fairly mundane capacitors. The crossovers in your speakers are likely far superior, such as in my case, where my JA Pulsars use the Modafferi crossover. By using the sub’s crossover, you are taking the signal from superior capacitors in your expensive preamp and forcing it through a mid-grade capacitor in the crossover before it is sent to your amp. That creates a sonic bottleneck, and actually degrades the sound. While there is some truth to the idea that running high pass through the sub alleviates some of the load on the amp and speakers, I think that placing the sub in the signal path really diminishes the sound overall and prevents you from hearing what your components can really do in synchronicity.