Update2: Nevermind the update1, question went far beyond its scope. Accepted answer was my expectation.
Update1: I have the filter(bandpass) design below, created using texas instruments filter design tool. I am also adding my specs to the question, in case it helps.
Gain at center freq = 1 V/V
Center freq = 1160
Passband width = 80 Hz( I figured lowering this made filter design more easy, more possible, though I would expect the other way around)
Stopband width = 400 Hz ( because of to be able to attenuate -/+ 300 Hz by 20dB, I chose 400 instead of 600 just in case, thinking about the non-ideal problems may occur)
Stopband attenuation = -40dB ( I have chosen 40dB just for in case, 20 or so is enough)
Allowable passband ripple = 1dB (not sure what this affecta, this was standard on filter designer software)
I can reach E12 resistors(%10) and E12 capacitors(%10)
These are the specs I have also used in the design tool.
The filtering action of the circuit below is close to desired. I have examined freq response with an oscilloscope + signal generator combination. I was expecting a gain close to 1 V/V , but it is actualy 0.15 V/V or so. Therefore, I want to increase the gain without affecting the center frequency. Is this possible? I have thought that gain can be arranged by the ratio of R5_S3 and R4_S3, and changed R5_S3 to 10k, but it did not affect gain, actually it did no difference, I can say.
So, I wonder which resistors can control the gain of this filter, if it can be controlled of course.