DIYAudio also has a store where you can buy a number of PC boards, parts and nice HiFi 2000 chassis's for any number of projects.  The articles Pass and Broskie publish include the audio circuits, power supplies and Bill of Materials (BOM), so you can source everything else you need from Digikey or Mouser who both have extensive on-line catalogs of electronic parts of all kinds.

I am in the process of building two new Pass Class A power amplifiers, a Pass / Sony VFET stereo amplifier which is similar to Nelson's FirstWatt J2, and an F5 Turbo, which is similar to Nelson's FirstWatt F7, a simple but very high quality MOSFET stereo amplifier.  I am keeping my Aleph 5 to see how well these amps compare to a single-ended Class A amp.  Nelson has indicated they should be comparable or better, being newer designs.  I have to say, however, the Aleph 5 is a very sweet amp and seems particularly well-matched to the Spendors !