I had DNA-0.5 Deluxe, DNA-125 and DNA-225.
DNA-125 and 225 sound pretty different. I had both at the same time. I liked the sound of DNA-225 much better than the 0.5 Deluxe or DNA-125 for that matter. It was smoother, deeper and overall a very nice step above the 125 with midrange and highs smooth and resembling the mids of DNA-0.5 Deluxe which I really liked. DNA-225 has some premium parts in critical places. DNA-125 doesn't.
DNA-125 sounded a bit colder in the highs and its bass was not anything to write home about. It was an improvement over the DNA-0.5 Deluxe in terms of resolution, but with sacrifices made in the mids(sounded less natural) and highs(sounded a bit more brittle). Soundstage size, precision and naturalness of the sound, well, DNA-225 wins all the way. I would either get DNA-1 Deluxe or DNA-225 for Totems. I'd skip the DNA-125. Unless your goal is to have sound on a cooler side of neutral, with an average soundstage size with emphasis towards high frequencies. I'm not a fan of revised amps as I think they focus on clarity and resolution, with overall musicality and natural sound being moved down on a priority list.
So to sum up on what I observed in my system with 3 amps:
DNA-0.5 Deluxe - very musical, excellent, natural mids, smooth highs, may be a bit less resolve than the newer series and less pronounced bass, but overall in a long run easier on the ears than the DNA-125. But doesn't come close to DNA-225. Nowhere near.
DNA-125 - better resolution than DNA-0.5 Deluxe, with a slight improvement in bass drive and detail, but a bit harsher nids and less natural highs.
DNA-225 - overall a champ by far. Resolution, musicality, depth of soundstage, bass, any area you pick it is a step up over the older DNA-0.5Deluxe and a nice step up pver DNA-125.
JMO.