I've owned both and still have the Rhea. Very different sounding units. The Rhea feels more stereotypically "tubelike". Warmer and more liquid sounding. The ARC walks that classically ARC line between a tube sound and SS sound. You get a somewhat leaner sound which feels meaningfully more detailed and articulate. Depending on the rest of the system (mine features an LS-25 and VT 130 SE) one or the other is likely to be a pretty easy call. In my system, the ARC was a little too much of a (ARC flavored) good thing.
BTW - as noted, the Rhea is MUCH more flexible.
One more caveat: Many early production Rheas (like mine) had noise issues. Jim did a no-charge mod for me, but if you're buying used, look for a later example.
Good Luck
Marty
BTW - as noted, the Rhea is MUCH more flexible.
One more caveat: Many early production Rheas (like mine) had noise issues. Jim did a no-charge mod for me, but if you're buying used, look for a later example.
Good Luck
Marty