As I recall it, the Forte 4a ran in pure class A, and was something of a classic design. If it were me, I'd keep it and get it fixed. I'll add that I'm not a fan of the Class D designs that I have heard; however, I do think you should give one a listen, maybe it would be what you're looking for.
Recap my ailing Forte 4a?
Any advice on whether I ought to upgrade my Forte rather than identify a newer design as a replacement? The rebuild will run me around $850 with shipping costs. I was considering a used Classe but it would be at least twice the price. My 25yr old Bryston 2B, which has been temporarily pressed into service, just doesn’t cut it.