I have to pitch in here as I regularly use my 1974 HH IC100 and 1x15 cabinet for pub gigs, there is no hiss at all and I have never needed more volume.
Cost effective too as I have used this setup since 1977, though the speaker has been replaced with a 300W Celestion since.
Back on topic I also have a 1972 Hiwatt Custom 50 which is as loud and clean as anyone could need and sounds good too, I tend to leave it at home as it is awkward to lug around and too valuable to get knocked about.