I can't compare the Rhumba to the Extreme, but I purchased a Rhumba 1.3 in December and am very happy with it. I upgraded from a Freya (OG) and you will not experience anything thick or veiled with the Rhumba, no hint of tubiness at all. It is really quiet, I have 98db efficient speakers and I have to put my ear right up to the tweeter to hear any hint of tube noise. With the Freya, I could hear some tube noise from my listening position. Andy at Backert Labs is a straight shooter, and I think he will talk to you about your system and make an honest recommendation as to which version to get.
Backert Labs Rhumba 1.3 vs Extreme
I am looking for a new preamp. I was curious about the preamp from Backert Labs. I saw some good reviews on them and they peaked my interest. My experience with tubes are limited, but I do have tube headphone amp- McIntosh MHA200. When listening to headphones, I always come back to MHA200 over SS amp. So I know I like tube sounds. Long ago I had Schiit Freya which was the only tube pre I had. I do not like veiled and thick sound sometimes I hear from tube gear. I prefer clarity / open / spacious sound with a hint of softness. I think the Rhumba can deliver the sound I am looking for, but just wondering if anyone has experienced the two models and share extra money on the extreme version is well justified. I will be hooking up the pre with Pass X250.8. Also I'd appreciate if you can comment on quietness of the preamp. Do you hear any noise when no music is playing?