any of the due beta stuff from the late 70's to mid 80's are excellent. The L530,L540 L550,L560 all Class A, and probably the best of the early 80's Luxman's and the direct predecessors of the current class A designs, if you can find one. I find the Luxman's that were the best are usually the ones with out the tuners aka receivers, their integrated and separates are very good for the 70-80's. Stay clear of the late 80's stuff unless you know what your buying as its hit and miss as the quality dropped after Alpine bought them in 86 (i believe 86 is right) some is good as it was a left over design others not so much.
thevintageknob will have a ton of information.
I ran a L560 Pure class A 50wpc and it was fantastic I think there is still some pictures on my profile (I should have kept it grr). you can find one of the L 530-L560 amps for around $1000-$1500 and they are worth it.
always factor in a re-cap in your vintage buy that way you will not be disappointed with the sound and when it enviably fails .
Some other options off the top of my head in that same quality bracket to think about are Accuphase, Marantz, Sansui, Threshold etc.