Sound Labs - Opinions

Ki, The older A-1s had impedances in the bass of over 50 ohms. A 500 watt transistor amp will only make about 70-80 watts into that impedance. So you were never able to tap the power of the amp with that speaker.

To really get Sound Labs to sing, you need a tube amplifier that will not loose significant power into the higher impedances. The older Sound Labs IME were easier to drive, that is they were fairly efficient, and their impedance was set high enough so that the speaker could be driven easily by a 100 watt tube amp. So, Rapid, If I were you, that is what I would be looking for at the very least.

Sound Labs A-1 are an American Classic.If they are in perfect working order you may find that you will be spending BIG BUCKS on other components to drive them.
If I had the room for placement and they were available to me I would go for it.

One of the problematic zones of some very old Sound Lab speakers is the contact between the connecting wires and the resistive membrane - made using a strip of aluminum sheet at the bottom of the panel. Sometimes the mylar membrane becomes damaged at this zone. Carefully listen for any noises in this zone.
I still keep the tweeters of my 30 years old A2's - although the bass panel suffered from this problem, the treble panel is still playing perfectly!
A friend of mine has a pair of A1s from the 80's playing perfectly.