Just want to clarify that the hardware requirements @Saqqara linked to are extension/user number based. That said, you'd have to first determine approximately how many users this system will host. You can check out our pricing calculator which roughly estimates the number of sim calls based on the number of extensions so you can maybe use this info as a baseline to then determine your hardware requirements: https://www.3cx.com/ordering/pricing/
I would say "Large" for both. 96 SC borders on needing 'Enterprise' specs but 3CX minimum specs tend to be generous, particularly with a Debian install.
The processor minimums haven't been updated for some time, it's worth remembering that the Gen 8 i7 was released 5 years ago and a Xeon E5 v4 is even more 'vintage'. So, for example, a modern i5 will give better per core performance than an 8th gen i7.