Look, they're never going to be happy so buy something that will actually deliver performance without being entirely offensive in terms of room presence.
A 12" cubed down firing sub is ideal, because you can always stand a plant (or something) on it and the best for sensible money is the
BK XLS-200 for £289.
If that's still not acceptable, then you really need to get a hold of your balls and insist that that there are two people who live in your house and both of them have valid opinions.
If that's another unrealistic proposition, then you need counselling, not an AV forum.
Russell
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Mitsubishi HC6000, 88" Carada Criterion, PS3, Sky HD, Yamaha DVD-S1700, Audiolab 8000CD, 8000AP, 8000M, 8000P, Rotel RB-985 MkII, XTZ 99.25, M&K Xenon Surrounds, BK Monolith DF, SMS-1.