@zlone Glad you liked the LA4. The Serene is a touch warmer and maybe preferred by some, such as this guy who compares the Serene to the HPA4 (same as LA4).
Review Holo Audio Serene Level 1 preamplifier - Tastefully Serene - Alpha Audio (alpha-audio.net)
I agree with this review but I like the LA4 the most still, but it really depends on the chain of gear it is hooked up to.
I like the LA4 and Serene so much that I tossed the shipping boxes. My preamp shopping days are done. I would not change these 2 for anything. I do not want sound added from my preamps, other gear in the chain already does enough of that.
I also have a Schitt Mjolnir (sp?) preamp. I got this because my Magtech amp does not have a Standby switch (long story). I think this preamp is the best one in Schitt’s lineup. It is sold as a headphone amp/preamp. The headphone amp is not powerful enough for my RAAL phones. I use the preamp with a Schitt Aegir amp and it is almost the best I have heard the phones.
I tried the Mjolnir in place of the Holo Serene in my office with the Magnepan LRS+ and Magtech amp. It was a real fun listen. Much warmer (but not too much). I was really impressed and it was definitory a better preamp for me than the Schitt Freya+ that I sold.