Why would you want to beat the hell out of a speaker that is designed for 600w? Even if it could take 1500w daily, there is no way I would EVER recommend doing it. As soon as something happens and it blows, the customer always wants to come and bash the company instead of taking the blame for blowing it themselves because they doubled the RMS power to the sub for now reason.
If you want to put 1500w to a sub, then get the Level 4s and you know you will be able to beat on it all day since the motor and suspension of the Level 4s are designed to take that type of power.
I know the limits of these subs very well and the Level 4 will suit you perfectly on 1500w per sub daily.