Tubes for Anthem gear

I just purchased a new Anthem Amp1 and Pre2L through Audiogon. Once they (and my ears) settle in, I would like to experiment with different tubes in them. Does anyone who has owned (and/or sold) these units have any insight into which new or NOS tubes work well with them, or Anthem gear in general? I'd like to know what different tubes may sound like with this gear, and if there are any brands/lines/models which are generally compatible. Thanks in advance, Steve