Shahzad:
Please obtain a book on opamp design techniques. This is the best way to mix the outputs to the speaker. Charles B. showed this in the last discussion we had on your subject.

Is this a one time hobby project? Or is this something you are trying to design for a production product?

Please also consider that the ISD chip may introduce distortion in the output if you unequally load the two outputs Out- and out+.

The best design of a product results from expanding our knowledge and learning the necessary skills to do the design the best way and not kludging the design to fit only what we know at the moment. As a matter of fact I approach every project as an opportunity to learn something new; many times taking on things to do that I know little about.

Michael Karas