Hello,
If the output of U1 is v1 and the output of U3 is v3, then the total response the way you have it set up there is:
Vout=(v1-v3)*R10/(R5+R10)+v3
and since you have both resistors the same we end up with:
Vout=(v1-v3)/2+v3
or:
Vout=v1/2+v3/2
So you are effectively summing half of each output response.
Now if you have an output near 0 for one and near 1 for the other at 0Hz, then the output will be 1/2 at 0Hz.
And, if you have an output near 1 for both near the center frequency then the output will be near 1 at the center frequency.
And, if you have the opposite responses from 0Hz at infinity then the high frequency response (given ideal components) will also be 1/2.
The phase shift from each however may change this, so we'd have to calculate that in too, which i will do later today if i can get to it.
The problem is that if they are both tuned to the same frequency then the phase shifts will cause them to add up to zero. So at 1000Hz you may get just zero output.
LATER:
Ok yes the two outputs cancel at the cutoff frequencies because the phases are opposite and the amplitudes are the same.
This means to get a bandpass you would have to connect them in cascade instead. Alternately, you could subtract them if you did not need too sharp of a response, but that probably would be a waste.