Just finished fine tuning my First Watt F5 clone.
I built it about a year ago out of parts that I had on hand back then, including a power supply reused from another project. The resulting sound was rather disappointing. Now I spent time matching transistors and tuning the feedback network. The amplifier now is very close to the performance described in the original service manual.
I am listening to F5 (the music is Tchaikovsky performed by Wiener Philharmoniker and von Karajan) and realizing that it is so good that if this was my first amplifier, I might not be interested in building anything else.
Update: after a year, this is still the best amplifier.
Update: I purchased the official F5 PCBs from the diyAudio store. I will rebuild the amplifier, hopefully with better FETs and other parts.