I've owned both the Atma-Sphere and the Joule 150(as well as the Joule 100 mk3). They are both fine but different.
IN MY SYSTEM, the Atma-Sphere's strengths were its ability to drive long cable runs thru its balanced outputs, clear articulation of complex music and natural timbre. It's relative weaknesses were noisier phono stage and quirky sensitivity(e.g. tubes that made noise, but tilt them slightly and problems disappears).
The Joule had a bit of warm tube coloration, which was pleasant, but less accurate. It also portrays a tremendous ability to convey the depth & body of each instrument. Phono stage was very sensitive to RFI, and this led me to sell it, due to living in a high RFI area.
Both are very holographic with big soundstage and good imaging.
FWIW, right now I'm using a Herron preamp and like it best of all.
I've also owned a BAT vk5i and would say it is not close to being competitive w/either the MP3 or LA150, although their newer and more costly models might be. Cheers,
Spencer