I've thrown my hat into this ring before in another post, so I'll be repeating myself a bit, but what the hell. I suppose good things bear repeating. I heard the X4s first at the Spatial shop with an LTA amp (I can't recall which iteration) and Benchmark DAC/pre, then, on a second visit, with the Don Sachs Valhalla. I then, at someone's home, heard the X5s powered by an Atma-Sphere S-30 amp and MP-3 preamp. While I was very impressed with my first listen of the X4/LTA/Benchmark setup, impressed enough to begin seriously considering revising my system, it was the second session, hearing the X4s driven by the Valhalla, that made my mind up and removed all doubt that what I was hearing was both better and different enough to warrant a wholesale (well, retail) revision of my system. Hearing the X4s and X5s driven, respectively, by the Don Sachs and Atma-Sphere amps was, literally, life changing. Not in the sense of making me a better person (too soon to tell; not for me to judge) or radically changing my world view, but in bringing about a fairly sweeping shift in my understanding of what hifi sound could be and causing me sell off this and barter that in order to accommodate my new understanding. After ordering a pair of my own X5s, I had the chance to hear a well-broken-in pair of them with the Vahalla, again at Spatial Labs, and that session convinced me to go with that pairing. I don't know that I could say with absolute confidence that the Valhalla is a better amp than the combination of S-30 and MP-3. My final determination is the result of a very uncontrolled experiment, as I heard each combination at different times, with at least several days, and, in the case of the X5/Valhalla combo, several weeks, between sessions and in different rooms. My no doubt unreliable aural memory tells me the presentation of the Vahalla was slightly (such cowardly adverbs themselves indicative of my uncertainty) more forward. Not that the sound in any way lacked depth, but it seemed (more cowardice) to present itself more than did the S-30, which seemed (ugh) both darker and more laid back. But these descriptors are wholly inadequate, possibly even deleterious, in that they imply, if forward, then shallow and bright and possibly fatiguing, if dark and laid back, then non-resolving and rounded off, none of which is the case. So, take those descriptors as the inexact efforts that they are. While I'm quite sure I could live happily with either setup, for those reasons, along with the craftsmanship of and parts used in it, and some other non-sound-related reasons, I decided to go with the Valhalla. One thing I am confident of: to my ear, both the Don Sachs and the Atma-Sphere outshone the LTA. One could object that the LTA was at a disadvantage being fed by the Benchmark. To that, I have no answer, never having heard the LTA paired with anything else. As with most advice on forums, I suspect this will more feed the flame of your uncertainty rather than do anything to douse it. I suppose that's just the nature of mining others' opinions. Then again, most decisions in life are made with insufficient data. I hope this at least adds a little more clarity to the picture. Good luck!