Jazzdude: I currently use the Cabernet - you will NOT be disappointed when you get yours! Note however, that all of Mick's preamps are very good and it is only a matter of degree as to improvements between the Syrah-Cortese-Cabernet.
Having said this, the Cabernet/Grange have an edge in having a 'hear through' character that is better than the rest. The sound of the directly heated triode (DHT) 101D tube in the Cabernet/Grange is unique and different from the 6SN7 used in the Syrah/Cortese. The 101D has a pristine clean signature coupled with a punchy accurate bass...no coloration, no smearing to the overall soundstage with all of the players standing clear of each other, each doing their own thing on stage within their own defined space. I am finding that the sound of 101D in the Cabernet matches very well the sound of the 6C33-CB power tubes in the Supratek Merlot monobloc amplifiers that I use, both having that supremely clean and effortless presentation.
Cello: the Cortese is a magnificent preamp and it is not surprising that you are happy with it. It has a wonderful tonality that just makes the music sound 'beautiful and alive'. Keep in mind that that even a stock Cortese is better than most preamps out there so while it is tempting to go for the upgrade you still have one of the best even in it's current state! Also, is the rest of your system good enough to show the improvements? In general, I find that only a good Electrostatic Loudspeaker will show you all the detail, nuance and finesse that the Syrah/Cortese/Cabernet preamps possess compared to other mediocre preamplifiers.
Regards,
Steve M.