Quad 405 - my first "audiophile" amplifer - sold to another keen audiophile some years ago, purchased used in the mid 1980's, ran with it for circa 20 years - gave me the possibly unrealistic expectation that a decent amp should have a lifetime of well beyond 20 years.
Quad 606 - lovely, powerful, smooth, compact, cool running - what's not to like.... (sigh, not enough current for my current speakers...)
Crown XLS2500 - a surprise how good these are, did not expect it. Still look at them with some suspicion at times - but my low impedance speakers are very happy when driven by these - capable of 1200W @ 2 ohm and bridgeable... thats a lot of Watts... runs cool and silent ... SINAD rates midlingly compared to current SOTA... but around the same as my Quad 606's - and these speakers sound better being driven by the Crowns. As a bonus I can feed them RCA, XLS or 1/4" jack inputs - and take outputs on bare wire, banana plugs, or Speakon