When I was auditioning the Spatial speakers at their shop, I first listened to the M3s and X5s powered by an LTA (I believe it was the Z10, though I'm not positive about that). I'd seen some videos and read some reviews of the M3, and, driven by the LTA, they were impressive, but not enough to make me want to switch from my Heritage Specials. Then Cloud hooked the speakers up to the Don Sachs Valhalla and I knew instantly that was the sound I wanted. While some aspects of an amp's or a speaker's sound may be demonstrable - soundstage, bass extension, etc - how one responds to or cares about those things is personal, and the judgement of overall sound is subjective, so (and, of course, I'm not saying anything you don't know) though it may be possible to point to certain things a particular amp, speaker, or combination of the two does "better" than another, it is impossible for anyone to say which a given person will prefer. That said, I far preferred the Don Sachs to the LTA. The tone was richer, the presentation more vital, more real, more present (I hesitate to say more forward, as that often has a pejorative connotation), but, mostly, it got my attention, not by being exceptionally clear or crisp or lush or any one specific quality, but by being engaging, immediately and unmistakably moving; I simply couldn't deny my response to the music, especially combined with the X5s. I was so smitten with this combination that I sold my Heritage Specials, which I loved, and bought a pair of X5s and ordered a Valhalla from Don Sachs, which I got about two weeks ago. It took about 5 months to get it - Don is building only part-time now - but it was well worth the wait. I'm new to tubes, so I'm sure I'm bathing in the glow of their newness, and some of that glow is no doubt being reflected in my writing about them, but there is no question the Valhalla demonstrably does everything better than my SS Classe CA-2300 (which is a fine amp) and is, in my admittedly limited experience, by far the best amp I've owned. If you want to bore yourself with more of my take on the Valhalla, I posted here on AC a revoltingly gushing panegyric on my first impressions of it under a post entitled Tube Newb. As many have said, they're both great amps. Reading everyone's opinions probably won't help you make a decision, but it's part of the fun. Good luck!