This dialogue about tubes vs. SS and low wattage vs. high wattage amps with Spatial Audio speakers has generated some very good information.
For clarity, I clearly understand that high efficiency speakers opens the door to a myriad of low powered amps. My main objective is to determine if I prefer SS over tubes with my Spatials. Period….
When I first took delivery of my X5s, I was using a PS Audio Stellar Gain Cell DAC (i.e., SS preamp/DAC combo) and PS Audio Stellar M700 mono blocks. The X5s were so new and all over the place with the break-in period, I immediately decided to replace the PS Audio with my current PrimaLuna EVO 400 preamp and amp. My auditory memory cannot recollect the sonic details of how the PS Audio compared to my current gear, but I know I like what I’m hearing much better. I actually bought a PS Audio BHK Signature preamp. It was decent, but I had a quality control issue with it and I sent it back for a refund. Done…. However, the speakers were still breaking in and I made so many upgrades in a short amount of time, I can’t tell you what component or cable made the improvements in the chain. I know better, but I did it anyway.

I have another PS Audio Stellar GCD in my second system with the matching Stellar S300 amp. So, several months ago, I employed that PS Audio Stellar Gain Cell DAC with my PrimaLuna EVO 400 amp while my EVO 400 preamp was out of commission for a few days due to a bad rectifier tube. I was using the preamp section only because I had my Holo Audio DAC in the chain. The PS Audio Stellar GCD sounded decent after settling in on its sound character, but it was “almost” like night and day compared to the PrimaLuna preamp. IMO, The PS Audio could not compete as it did not have the bloom and airiness of the EVO 400. I could say more, but I will spare your time. I couldn’t wait to get the EVO 400 back in the chain. The entry level PS Audio Stellar GCD is probably not a fair comparison to the EVO 400, but that’s the SS I have in house to compare with tubes.
Then, I had a recent, in home, shootout between the LTA MicrozotL preamp and ZOTL Ultralinear+ amp vs. my PrimaLuna EVO 400 preamp and amp. I loved the detail and the handling of vocals over the PrimaLuna, but it seemed like the PrimaLuna had more bloom and weightiness. I’m hopping to find a preamp/power amp combo or maybe an integrated amp that offers the mix of the things I liked with both the LTA and PrimaLuna gear. I’ve heard that Luxman was very detailed, but smooth and all the other flattering adjectives that audiophiles like to use. So, I zeroed in on Luxman. I got a feeling, I need to stick with tube gear, but I can’t confirm it until I audition a good SS preamp/amp or integrated with the X5s.
I have recently heard positive chatter about Atmasphere tube gear as well. Lots of fun, but I just need lots of time and money.

Thanks all because your input has been great!