I had the Fire Preamp in my system for a few days. It is big, heavy, and runs hot. I don't know what is inside, but the sound screams MOSFETs. If you like second order harmonics that suggest a "tube" sound, then you will probably like it.
I dislike the veiled and hazey sounded created by MOSFETs in general. This preamp wasn't to my personal liking.
Henry is a wonderful person and the build quality of his equipment is top-notch. Our audio tastes and expectations are just different.
Whimby