Lee (webby) asked me about mods for his audiolab 8000 amp.
I've obtained a schematic from one of the other forums.
Assuming it is the same as yours Lee, I'd start with PSU smoothing caps (dependant on age (Black Elna in pic but not on diagram)). There is a cap on the input (c101 1uF) that would be worth changing to something decent (I like Mundorf Supreme). Amps aren't really my thing but I'd start changing the components in the signal path for 'better' parts. Resistors to something like RC55Y welwyns maybe.
Any other suggestions welcome!