Both are Thiel speakers,the SC6 is,I believe rated at 86db and the new 3.7 at 90db.I have heard the 3.7s through three different amps,Krell and two different Classe,one of which was mine.The SC6 I heard through an Arcam 85 amp, in a barren unfinished basement.Of course the 3.7s did sound better in the perfect listening rooms,with more power,however the 3.7s cost more than double the amount of the SC6 and the SC6 is in mint condition.