So what is the most powerful (but stable!) CPU to use with Cubase?

Not really that hard. I told you to read the statement closer, and apparently I remembered it differently. Like I said, if it’s as clear-cut as it indeed seems then I and others would have “drop-outs”. If we don’t then the statement isn’t correct.

If you read the post I linked to it says:

DAWbench, RXC-EXT results:

Buffer: 32 samples
RXC-EXT: 213 instances
ASIO-Guard: OFF

Buffer: 32 samples
RXC-EXT: 320+ instances (end of DAWbench tracks)
ASIO-Guard: ON

Buffer: 128 samples
RXC-EXT: 256 instances
ASIO-Guard: OFF

Buffer: 256 samples
RXC-EXT: 294 instances
ASIO-Guard: OFF

Those were the limits for those settings. So, with AG off at 64 samples I would expect between 213 and 256 instances of the RXC-EXT plugin. More importantly (for me), with AG on I got far more plugins than I normally need, and I’d expect to get far more if I kept going, so I just stopped. Mind you I don’t do any VI work so latency isn’t that important to me. 128 or 256 is more than fine. Probably 512 as well.