power line conditioners...

When I worked in high end audio, our guru placed a 120v-120v transformer (heavy duty -- 1000va) between the wall socket and the power amp in the system being auditioned. This was just before power line conditioners became available as audio system accessories.
I found a Sola 500va 120-120 transformer in the trash and tested it -- it worked. I tried it between the wall socket and my power amp. The sound stage opened up. Also, bass was tighter and more authoritative. I felt like the high end was also clearer. I am using a Dynaco st70 in triode mode driving Kef 102's, a dynaco PAS-3X, a VPI MK-IV turntable with an Alphason HRS-100 arm, various cartidges, and a Micromega Stage3 cd player. As my room is rather small, I don't feel the need for a sub-woofer now.
I wonder if any of you other members have any experience with PLC's, or Sola 120-120 transformers? And if you have any thoughts on why the sound is improved. Could it be simply reduction/elimination of voltage fluctuations coming from the wall, or are there other things happening like availability of stored energy in the transformer for musical peaks or transients?
Another question that I have is how are the audio-specific PLC's different than a 120-120 transformer? Are they different? Are they worth the extra money?
After hearing the differences that the Sola made, I am convinced that there is something to be gained from power line conditioning. I just don't understand it very well now, and would like to!
Cheers!