It would be quite tricky to get the levels right, as most automatic setups are not set up to deal with 2 subwoofers dealing with different frequency spectrums. I suggest trying just the SVS, and if that works well, then just forget about the other subwoofer. Sell it to someone else, or give it to Goodwill, but do not use it if you do not need it. (If it does not work well, post again, and send me a PM if I do not seem to notice your new post.)
As for dealing with your wife on these things, I strongly recommend strict honesty, and also trying very hard not to get suckered into any nonsense in audio. My wife is okay with the things I do, because I do not waste money on magic wires and other nonsense, and I am strictly honest with her on why something has to be as it is in order to work well.
Many years ago, my wife asked me about those "cute" little Bose speakers. I explained to her why they are not good and cannot be good. She was okay with that, because I do not lie to her about anything, and I do not believe in nonsensical magic in audio or other things. After some time, we attended a party at a coworker's house, that had the little Bose cubes, and, without me asking about them or saying anything about them, my wife commented on how bad the little cubes sounded.
If, however, you try to manipulate your wife in some way or other, if she is smart, she will stop believing anything you say. So in the long run, it is good to keep to a policy of strict honesty, and to avoid BS nonsense, because if she is smart, she will not like it if you are suckered into some nonsensical beliefs that waste money and make your home look bad.