The LK 140 is the older of the two, I have never put them side by side, but owned seven of the 5105's for a while, very good amp, very musical and smooth.
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AV5105, introduced June 1996, discontinued March 2002
LK85/LK140, introduced March 1998
Looks like LK140 is still in production while 5105 is not.
AV5105 supports more speaker output than LK140 (4 pairs vs 2 pairs).
AV5105 has on/off switch at the back, while LK140 has it at the front.
AV5015 sold at $1800 in US and LK140 at $1300.