A Recording Interface is not an Audio Accelerator, and even companies like UAD have their own challenges with DSP power in this regard, limiting the number of plugins that can be used. The problem with audio processing is that it needs to be done in real-time; you can't buffer it at will. The more and the more CPU-intensive VSTi and VST plugins you use, the more computational power your computer needs to process the data in a timely manner.
That's why, in a project, you may need to increase the ASIO buffer size (or use different buffers on Apple devices) to give your computer enough time to calculate audio data and perform I/O, or else you may experience audio dropouts. Additionally, Windows and macOS operating systems were not originally designed for real-time tasks. While they can now handle many tasks "within their capabilities" quickly, there are no guarantees about when these tasks will be executed.
Adding to the challenge, low-level routines (drivers) on CPUs are generally given priority to ensure data integrity in non-real-time operating systems. A running driver cannot be interrupted by the process scheduler; driver code can only interrupt itself and release a CPU core for other tasks. This works to varying degrees depending on how well the CPU is suited for the task (Single Core vs. Multi-Core Performance) and the quality of the drivers (DPC Latency). In the worst case, even the fastest computer can be slowed down by poor drivers, making it unsuitable for real-time audio processing.
This is just the hardware side of the issue. There's just as much that can go wrong in the realm of application software:
1. poorly written DAW software
2. CPU-hungry VSTi/VST plugins
3. poor or inefficient project organization, and
4. how well a DAW can utilize multiple CPU cores.
Regarding these points:
to 1. For poorly written DAW software, I would recommend sticking to established products from reputable manufacturers.
to 2. In the case of CPU-intensive VST and VSTi plugins, research which ones exceed the usual performance requirements or latency expectations. You should either avoid them or consider freezing tracks by precomputing audio data and saving it as a WAV file, so your DAW doesn't have to repeatedly calculate it in real-time. DAWs like Cubase offer extensive features for working with frozen tracks.
to 3. Project organization is critical. If you use many inserts on a track, they will be processed serially one after the other by a CPU thread. If these VST plugins are also CPU-hungry with high latency, it can significantly add to the required CPU time. CPUs with a high core count but low single-thread performance can struggle to calculate data in time.
to 4. Pay attention to how well your DAW can distribute the workload across CPU cores/threads. Not all DAWs are equally efficient in this regard.
When selecting a CPU, don't just focus on core count; prioritize CPUs with high single-thread performance.
Now, returning to RME, here are the key advantages for your situation:
RME recording interfaces do not rely on third-party I/O components; communication with the computer is handled through the internal FPGA chip. This chip can be reprogrammed via a flash operation. Combined with excellent drivers, this provides a solid foundation for any RME product, whether it connects to the computer via PCIe, Firewire, or USB.
While it's true that an interface with fewer I/O ports requires less bandwidth for the transfer between the audio interface and the computer (typically, all tracks are transmitted, whether in use or not), this is usually a concern for low-quality or poorly configured PCs. Therefore, I wouldn't be deterred from purchasing a UFX III if you need its ports, features, and I/O reserves for future expansion.
This is a complex topic, and I would recommend working with a company that can provide comprehensive guidance in the following areas:
1. Choosing the right DAW product and project organization, possibly testing with a demo project.
2. Building a turnkey computer with suitable components, potentially testing with a demo project to determine which CPU handles the workload best.
3. Providing support for optimizing your DAW projects.
I hope this helps!
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14