It does not surprise me that someone would greatly prefer a Supratek over a First Sound in a given system.
I don't believe all pre-amps mate electrically with all power amps in a way that actually allows the two parts of the signal chain to perform under optimal conditions. Even though designers and engineers will tell me that I am completely wrong, my experience has suggested otherwise. Components should work well with other components across a wide spectrum, of course, but the balancing act that takes place between stages in the signal chain can be less that optimal.
The First Sound pre-amps have minimal circuitry: a single gain stage, no buffer- or cathode follower stages, etc. As such, they have a relatively high output impedance (1300 Ohms or so) and medium gain (16 dB). Sometimes, this can translate into a "laid back" quality with some power amps. The power amp should probably be fairly sensitive at their inputs (say .75 - 1.2 V) to work pretty well with the First Sound. With decent matching, the First Sound is very dynamic and alive--with out being "in your face."
Conversely, some pre-amps over-drive the inputs of some power amps and do indeed slam everything at you. Long story here, but I believe I have encountered both under-drive and over-drive from pre's to pwr amps.
Like any component, and perhaps even more so in the First Sound's case, it has to be matched with the associated power amp(s), and it also responds greatly to changes in power cords, interconnect, and isolation devices. (Part of its minimalist approach makes it this way, maybe....) This matching requirement may not be as critical with the Supratek; it looks like it has more active circuitry (just a guess by all the tubes). Also, a system "tuned" for a Supratek may have precisely the wrong set of cables, power cords, rack, and the like for the First Sound and vise versa.
I don't suggest that one way is any better than the other: absolute minimal circuitry vs. more complex, active circuits. Proof is in the result according to the designer's goals and chosen compromises. I have no ax to grind either way.
The Supratek Syrah I had hoped to audition next to the First Sound was sold by its owner only a matter of days before I made the request to hear it. I will keep trying to get a side-by-side listen of the Supratek, though.
