adnan_m_s,
Do the calculations, as audioguru says it will produce 7W of heat, most of which will be in the MOSFET.
Heatsinks are rated iby their thermal resistance (°C/W), a 1°C/W heat sink will rise by 1W above ambient if the when dissipating 1W or 2°C above ambient when dissipating 2W.
Also take in to account the thermal resistance of the MOSFET juncion to case and any insulators between the case and the heat sink (just add them all together).
You want the MOSFET junction to remain below the maximum operating temperature when dissipating 7W at the highest ambient temperature that you want to operate your design in.