I have never had or heard a Mainline, but IMO, for dollar value, the S3X amplifier has to be one of THE best tube amplifier's ever created. I have had many solid state amps and a dozen tube amps. What I use now and will for the future is a Crack/SB and S3X. I run an HD 600 with Crack and currently using a bombastic Denon AH-D7000 with the S3X which is unreal. A Moreplay (outstanding) is used with a power amp for speaker listening. I am not sure people appreciate how outstanding BH gear is. Enjoyment factor is high, I always like flicking the power switch to the ON position.... satisfaction guaranteed ....