That would help with the cpu, but it would cool the VRM less. Your main concern would be the VRM on the motherboard overheating.
It is designed for 95 watt CPUs. Which you already have. Once you start overclocking the voltage requirements jump substantially.
Mine overclocked @1.4 volts pulls between 160 and 177 watts, which your motherboard can not handle . It does not have active cooling on the VRM.
The stock heatsink blows down on the motherboard, which helps keep the VRM (located between the cpu socket and back panel connectors ) cooled. The tower heatsink will not help with cooling them, as the air will be over and not through them.
In the end the decision to overclock is yours. I have been doing it for 19 years with great results. BUT you have hardware limitations which must be taken into account.