Rob Sands in Scouseland had one to try in his system and he borrowed some valves to try in it from me (Mullards) and when I heard it, it wasn’t great (std one), the foo valves made a bit of a difference, but not much. To my mind, the MM stage in my Croft Super Micro is better. Rob eventually bought a SS stage (Trichord I think), which sounded a lot better.
Not heard the R. With Croft stuff it changes all the time, so you have to get the right generation.
Shame you are not closer, as you could borrow a couple from me.