Aspen Amplifiers, http://www.printedelectronics.com/ Hugh offers various preamp and power amp designs in kit form. His AKSA 55w power amp paired well with my Klipsch 10.5's and Aspen's customer service is top shelf before and after the sale.

Pass DIY, http://www.passdiy.com/ If you are interested in Class A solid state this "is" the place.

White Noise Audio, http://www.wnaudio.com/ Because our dollar is so weak against the Euro and UK pound this company is at a distinct disadvantage in the US DIY market. It's ashame because WNA does have some rather interesting designs.

To answer your other question the AKSA uses bipolar or BJT's in a fully discrete push-pull topology and operates in Class AB. More info can be found on Hugh's site.