I would strongly suggest that you don't need a core with a low differential to imitate the ball reaction of the IQ Tour Pearl, from 2 aspects. One, you could always use a drilling to reduce the differential of the core, and two, the IQTP has a rather special combination of R2S and a core. While I haven't seen many Marauders and Recklesses locally, I've seen ton of IQTPs with a wide variety of drillings thrown by a wide variety of bowlers. They get a large variety of reactions. I'd e very surprised if one of them could not be made to emulate the reaction of an IQTP.
That said, if you want an IQTP, I agree with Urethane Game, get one.