Probably cost more to fix than it's worth? Unless it is a very simple fix. Still and all, tech will charge his time. Since it is a 'slow death' and apparently agonizing it could be caps. Has it ever overheated or simply run too warm? or gone into shutdown? Driving which Magnepan? Which B&W? Maggies like lots of power and the B&W is not exactly the easiest load. Neither speaker sounds like a good match for the Yamaha, unless you don't run it very loud, when you may be able to get away with it.