Restock,
I'm surprised at your experience with the Rhea. I haven't heard any of the stages you mention, but I've directly compared the Rhea to:
ARC PH3se
Herron
Klyne
Aesthetix IO
Lehman Black Cube
BAT PK-10
Putting the Io aside for a moment,
IMHO, the Rhea easily outperformed each of the above in every way meaningful to me - other than noise (some of the comparisons were done before the unit was modded). It has beautiful "bloom" and tonality, imaging is the best I've heard (except for the Io) and deep bass is astonishingly good - FOR ME, better than all of the above - including the Io. After the mod to bring the Rhea to current spec, it's pretty much dead quiet - so I doubt noise is a meaningful issue now.
The Io sounds great, maybe marginally superior to the Rhea in stage depth, but FOR ME not significantly better than the Rhea in any other way. The Io had a darker character through the mid bass that I found less convincing, and it's also bigger and obviously much more expensive.
I also had a less controlled opportunity to compare my Rhea to an ARC Ref Phono and preferred the Rhea again, but there were enough uncontrolled variables to make this conclusion less reliable. Overall, IMHO it's the best sounding phono stage I've heard. Obviousy, YMdidV.
Other than the ARC Ref audition, I mainly used an Oracle, Graham 2.2, and Transfiguration Nightingale or Lyra Dorian (on a second wand) for my comparisons, although an Acoustic Solid Table with a modded RB-300 and Clearaudio cart were also employed from time to time.
Marty