Hi Thf,
Sonically they are very similar but the Cortese is more refined, precise and has better bass extension. The highs are more controlled and sweeter with the Cortese. The tonal balance of the mids is difficult to distinguish between the two preamps.
Overall both preamps have the same family sound but in an effort to describe the subtle differences with words I will undoubtedly create a scenario which is more exaggerated than is true. Ready for an exaggeration?? Here it goes!!The Syrah sounds more immature - like a rambunctious child compared to a more mature, strict and disciplined Cortese.
Done exaggerating.
This type of improvement is typical in high end audio when upgrading any component within the same manufacturers line.
Unfortunately the area where there is the most significant improvement between the Cortese and the Syrah is in the overall quality of the unit.
For whatever reason, the Cortese has zero microphonics, zero hum and/or buzz. The Cortese is not as sensitive to tube quality and less sensitive to where its power supply is located. The Cortese does not rattle or vibrate internally - it's heavy and solid - like it should be.
The Cortese seems like a better perfected high-end component whereas the Syrah, to some degree feels like a high-end "DIY" type of component.
Awesome results can be achieved with the Syrah but its subtle quirks can overtly effect the sonics if extra care is not taken in tube selection, positioning / location of the power supply, relation of the preamp to other components, etc.
Is it worth the extra money? I think so.