Besides stellar sound in a preamp, I also look for reliability, ease of use, tube rolling potential, great communication and helpfulness, attractiveness, an available upgrade path that is cost reasonable, and synergy with my other equipment. So far AH has fit this bill beautifully.
I know for me things really dialed in with the AH with an exceptional quad of Seimans NOS early sixties cca's. Other quads of cca's and other tubes just didn't do it as well for me. Victor confirmed my judgment of the cca's that I ended up with.
I am eager to hear equipment such as the Dude and the Sampsons that are reported as taking things even further but the incentive to chase the next best thing has been greatly diminished when it is so much fun to listen to what I already have and I am so pleased with the customer service.