Well with that shot it can destroy two Land Raiders and still kill a guy or two on the other side. Which would be cool if they could do that.
But back to topic. The 4d6 with the Monolith is a huge grey area but the rule for living Metal says any additional dices can't be use but the Turbo shot says its use 4d6 base armour pen so its really hazy, foggy, cloudy, grey, and alot of other terms about what is done here. Really until the new Necron codex comes out or GW FAQs it we will not know and I am guessing it will be ironed out in the Codex and anyways we don't know that the Monolith will have the Living Metal rule in the new codex or not.