Some layouts aren't "ready-to-etch," meaning you might need to recreate the PCB designs in modern software like KiCad if you're sending them to a fab house. (PDF) THE AUDIOPHILE'S PROJECT SOURCEBOOK
Slone’s designs are technically more robust and higher power, but significantly harder to build due to the complexity of the PCBs. They are engineering marvels designed to measure impeccably on an oscilloscope. the audiophile 39s project sourcebook pdf