I went from a PH7 to the Ref Phono 2 to the Ref Phono 2 SE. Find my somewhat understated comparo between the PH7 and the RP2,
here. You're part-way there inasmuch as the PH8 uses the 6H30 in its amp section versus the 6DJ8-family used by the PH7. Taking the next step, you're right, the RP2SE is indeed a destination component and you are in for a real treat. No doubt you can find reviews of the PH8 and comparisons between it and the RP2 and RP2SE, but in a nutshell, the SE brings: nice improvement in bass weight and definition, richer tonality with more harmonic information, greater image solidity, improvements in soundstage information and a sense of dimensionality and space. Overall, it is more transparent with less distortion than the PH8.
Like everyone says, break-in takes ~600hrs. There are a variety of
options including various
CDs that expect you to connect your disc player to the phonostage and play repeatedly. Wally Malewicz sells a complete phono burn-in
system that covers tonearm wiring, phono cable and phono stage. If you go through a burn-in regimen, this would be a good time to get out your setup tools and review your tonearm and cartridge parameters: VTF, SRA, Azimuth, anti-skate.
Enjoy your new Ref Phono 2 SE!