if i were to replace the fans, i would have to match the air flow of intake and exhaust?
No. Your case can also have either positive or negative pressure. Mine has negative pressure, where my 2x140mm exhaust fans move more air than my 2x120mm intake fans. But that additional air has to come from somewhere, so it pulls air in through the vents/grills. Positive pressure would be the opposite, where more air is coming in than escaping, so the excess air would be pushed out through vents/grills. Toms just put up an article explaining it in more detail.