You can't go wrong with either Quad but I'd personally go with a 63 too just because they are easier to live with. You shouldn't need new protection boards but diodes do age and components drift so why not get a new set. Better to spend a bit here to be sure they are protected.
There are a lot of good Class A amps out there and even more amps that remain in Class A for the first few watts. Old Krell, Pass, Bedini, some of the Accuphase amps and the list goes on and on.