I see you started in 1979, presumably the launch of the paper magazine. The Quad 405 was on sale during this period, up to 1982. It - and it's Mk2 version, are still regarded as amplifiers of the highest quality, so much so that they were power amps of choice for many small recording studios
The recording engineer/producer of a selection of albums by Mike Oldfield, inc T.Bells, is a friend of mine. When he built his mobile recording unit 'The Sound Box', a Quad 405 powered each channel of the monitors.
This quality of recordings of this mobile was sufficient for the London radio station LBC to engage it to record the classical music strand of LBC's output. The Quads, powering Tannoy 'Little Red Monitors', were of broadcast monitoring quality.
405's are still much sought after. They have become legends of the power amp world.