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

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.

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.

@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.