Hi Redkiwi, Bruce Wenger at BWS, has the Amperex tubes you are asking about. His phone number is (703) 536-3910, and his web site is: http://bws-tube.com/ You may e-mail him from that site for specific information. I have personally known Bruce for many years, and he is not only a wonderful person, but a highly skilled designer. I agree with Reprince comments about Andy Bouwman as well. Both of these guys are among the very best in the business. By the way, the amp featured on Bruce's web page, the BWS 845, is a hand built product by him. I did much of the artwork on the shape of the faceplate, the BWS logo and the script (typeface) and placement of same for this amp. I also did the photography of this product, featured on the site. I also do photography for Andy Bouwman, and am currently waiting on a new project he is developing, I will post about it when that happens, with his permission. I can confirm that both these guys are a wealth of information on matching tubes with components. I am sure that one or both will help you achieve what you are seeking. Best wishes!