They're not. To my ears, the Opus#2 sounds more balanced and leaner than my previous DP-X1A, and Aune M1s. Opus#2 just sounds technically better, being more transparent, and resolving. It has a higher level of details, and resolution, with the tone having more emphasis on clarity than warmth. It's a relatively uncoloured reference DAP that is also smooth, sounding less harsh in the top-end than DP-X1A, and M1s. The DP-X1A has a slightly more bump in mid, or upper bass which makes it sound less airy in the treble/upper-mid frequency. It does have a good sparkle, however it sounded less natural IMO. The M1s has more sub-bass rumble, but it sometimes sounded a bit peaky in the upper region.Soundstage, the Opus#2 is the largest of them all. Each notes have a higher (lifelike) definition, and a very good separation, plus positioing (width, and depth). The tone is slightly less warm than most DAPs, less intimate, and emotional; instead more neutral (with excellent high-resolution, and details).
I'm still curious though how the Opus#2 compare with WM1A in sound. Tried searching this thread, but only found a few useful comparisons.