SEARCH, Keith, Search; you'll learn lots.
Briefly, I've found the (expensive) Tung-Sol RoundPlates to be the best 'N7, with the 'Canes' 1st (middle) tube highly sensitive to tube microfonics. Ken-Rads are a great-sounding and less-expensive alternative.
I've been using the Penta/Shuguang KT88SCs; they sound great and are more reliable than the ValveArt '88s.
http://www.pentalaboratories.com/Product.aspx?dept_id=5020&pf_id=KT88SC%20SHUGUANG
.
Briefly, I've found the (expensive) Tung-Sol RoundPlates to be the best 'N7, with the 'Canes' 1st (middle) tube highly sensitive to tube microfonics. Ken-Rads are a great-sounding and less-expensive alternative.
I've been using the Penta/Shuguang KT88SCs; they sound great and are more reliable than the ValveArt '88s.
http://www.pentalaboratories.com/Product.aspx?dept_id=5020&pf_id=KT88SC%20SHUGUANG
.