100% go with the Patton, you are going to have no chance of getting support for Digium products with 3CX.
The Patton 4970 could be an option however depending on your setup you might require one of the gateways with the high precision clock so please provide more information reference how you are handling the migration.
The high precision clock models might be used for example in a scenario where you are migrating a system and not retaining any ISDN connections, you would then use a model with high-precision clock so it can provide the clocking to a legacy PBX.
If at least one Telco ISDN connection is retained then you don't require the high-precision model but these models do have an extra port also which gives you flexibility in a scenario when you are connecting a legacy PBX to SIP trunking whilst retaining one Telco ISDN connection for failover and clocking.
Let me know more detail and I can provide you with the best model.
End goal is going to be to have a ISDN connection feeding into 3CX via a gateway, having the ability to slowly migrate over between now and then would be nice but isn't a dealbreaker.
If you want to transition slowly and migrate from one system to the other then you would need a model with multiple PRI ports so High precision clock version is required.