Hello @bobheinatz
i have (and still own) a pair of 15ohm Rogers walnut 3/5a(1990) and a pair of Harbeth Rosewood (special edition) 11ohm (1994)
1. I found them perform the best with Foundation speaker stands , without a proper stand , they don’t throw a “larger than box” soundstage. With proper stands and placement ( and high current amps) they can be a profound experience.
2. They produce the sweetest vocals when paired with tube amps imho, I used Jadis , Conrad-Johnson amps back in the 90s and no other ss amps can produce that density and fluidity , that’s why I think many audiophiles are so addicted to 3/5a and I had seen people using 000thousands worth of equipment to drive them.
But the downside is at the end they are bookshelf and BBC designed them for close monitoring at remote sites. They don’t can give you a full orchestra experience or the lowest frequency due to physical limitation.
Be willing to feed them with high current amps and they will reward you greatly !
3. If you are after vintage 3/5a be sure to check the seals are still flexible. Different brands seem to use better crossover components and different veneer produce slightly different SQ ( the rosewood / ebony can go a little deeper bass, walnuts tend to give a more relaxed vocals)
above are just my personal experience, enjoy the journey !