CCM or MDM?

We currently use EBP version 3.0 - classic scenario, with a Requisite catalogue. We are about to upgrade to SRM 7.0. I had asumed we would use CCM version 3.0 for the catalogue. I have now read a lot about MDM, and am wondering if we need CCM and MDM, or has MDM replaced CCM?

If MDM has not replaced CCM, why would you use MDM instead of CCM?

If you use MDM do you need the search engine TREX?

Many Thanks

Claire