@johnnycopy
The Frankensteins are marvelous sounding but can be a bit hard on the 300b tube. I had two failures with the excellent Takatsuki tubes within a 5 year period. Admittedly I use my Frankensteins very regularly for long listening sessions (4-5 hours on average). The EML XLS has withstood this usage well over 9 years with zero problems and continue to test well.
Obviously I can’t predict what your outcome will be, but the point being that the EML has many owners who’ve had very similar experiences as mine over the years. This refers to their “solid plate “, not their “mesh plate tubes. The mesh is very spacious and airy sounding but is much more delicate with regard for usage. XLS is a heavy duty rugged workhorse 300b yet also sounds superb in my opinion.
Charles