Dual Sub-woofers paired into two sets of speakers - connection option.

If your subs are powered, then the speaker level inputs will go to a line level converter before going to the sub’s plate amp. This will present a high impedance connection compared to your mains. 
 

Speaker A output to R/L mains and Speaker B output to R/L subs should be no problem.
 

Folks use dual mono subs driven off a sub or preamp out so they can position and adjust the subs to null out room nodes. For many systems this produces better results than true stereo subs. Lots of reading on this subject is out there.

A another consideration is high passing your mains to 1) better integrate with the subs and 3) take the bass load off the mains. I use this approach with great results.

good luck and enjoy

@tunehead .... Do both. SVS and us....
It'll be interesting to compare/contrast the results.... ;)

Knowledge can be a terrible thing: 

Either makes' your day or ruins it. *L*

Why are you asking the people on this forum?

Why not talk to the people at SVS? Here you will get educated guesses. The manufacturer will give you answers.

Let me see if I understand this. Sub 1 (S1) will have A left and B left connected as inputs, Sub 2 (S2) will have A right and B right connected.

In each case you will keep the A and B wires separated and they will go to the sub’s L or R inputs?

What you shouldn’t do is connect L A and L B through S1-Left input. That would not break anything but you would lose your A or B switching capabilities. :)

The remaining thing which might cause an issue is if your amp was bridged.  That is, if both (+) and (-) were driven, which sometimes causes problems with subs that ground the (-) inputs.

your parasound is a high-current amp designed to go down to 2oHm, so unless your speakers are ridiculously demanding i wouldn't expect it would have trouble driving both sets of speakers. i also see no problem with connecting one or both subs via the speaker level input on your amp. that said, i'm not sure whether you'd achieve better sonic results with two sets of speakers and/or whether your two subs would sound better via speaker level connection vs. your current lfe connection--i suspect it's system-dependent. rel subs, for one, tend to sound better with speaker-level connection; others may not.

@tunehead   Correct in your thinking. High level connection will pass along the sound charateristic of your amp. Punchy amp = punchy sub.

It uses a small signal and uses no extra load. Highly recomended for stereo set up.

@loomisjohnson 

Thank you for your response,

My power amp is a Parasound 2350 class D, 600 watts x2,

• 350 watts x 2 @ 8 Ω
• 600 watts x 2 @ 4 Ω or 2 Ω

Minimum Speaker Impedance (Output A+B)

• Stereo or Mono Mode: 2 Ω 

I like to experiment, but am very cautious. I was of the understanding that connecting a sub up to the speaker level input from the main speaker yields a more coherent signal being the exact same signal that the speaker see's but presents virtually no extra load, the sub still does the power amplification and cross over processing. Am I correct on that? Think I'll try with just one speaker set and let my ears inform me.

@livinon2wheels Thank you for your very thorough response. Maybe a little over my head but I do get the gist of it. Really just want to know if I am opening up the possibility of damaging anything (as @loomisjohnson  noted, possibly if running both A and B at the same time). I'm just curious and will try with just one speaker set. I was of the understanding that connecting a sub up to the speaker level input from the main speaker yields a more coherent signal a it is the exact same signal as the speaker see's but presents virtually no extra load, the sub still does the power amplification and cross over processing. Yes, try it and listen. My ears will tell me. I like experimenting.

you haven't specified what your amp is, but i'd be very hesitant to run speakers a and b at the same time--you're effectively halving the impedance load that the amp sees, which could potentially damage it and will likely affect performance.

Rob I would do that if its convenient, or at least I might would. :) Think about it this way...I have no clue what your crossover frequency is, but the lower that frequency is, the less directional the bass is going to be in general. There are exceptions to this but its a pretty specialized situation. Lets say your crossover is at the standard 80 HZ crossover that Dolby has used for decades. At frequencies below 100 hz that are in phase with each other between the left and right channels, directional cues for where the bass is coming from are going to be largely nonexistent. But if there is a significant phase difference between the left and right low frequency channels ( not all that common ) you will get directional cues from that phase difference. Most material does not have this phase change as a part of the mix. So connecting up using speaker inputs on the subs so you can appreciate those phase changes is going to allow you to experience that, but prepare to be underwhelmed. As it currently stands your single sub output provides low frequency support from both subs with the signal spread over both drivers in the two subs. By making the change you are considering, now you may not get the additive support of two subs from the same signal, each sub will be supporting the listener by itself or certainly not in lock step with the other sub. Now the signal will be split between two channels, divided, and your overall room response may very well suffer for the change. Maybe that is a trade-off worth making in your estimation. Does directionality in the low frequencies count more than output and low distortion? Only you can determine that for your ears. The only real way to find out is to test it and see if you like it better. If you do, then you are one step closer to nirvana. :) If not, going back to what you had will be an improvement and you will know that making that change was not a great one for you.