I own many RCA Living Stereo recordings, and I agree, some sound spectacular. I found a crap load in decent condition at a record store near where I work. I think I bought like 15 of them in one shot there, paying on average $3.99 per Lp. Others I acquired from both Ebay and discogs.
One thing I have learned is that on occasion, the white dog labels sound better than the shaded dog....for instance Sheherazade...
The Phase 4 Lp's sound great as well, I pick them up whenever I come across them in good condition.