Hard to go too wrong with those options. I can say the Claytons make everything sound like music. I thought about replacing them with some high powered Cary amps a year ago and the Carys, while good amps with very good bass, were not even close in musical enjoyment, IMO. These are very different companies with Clayton being basically a one-guy outfit and McIntosh being a larger, more established audio company. However, I think the build quality is very good for both. Wilson is a great guy and a no-nonsense designer. With Clayton, your money will go into the parts and resulting sound quality, every aspect is robustly designed and constructed to last for many years. Wilson has even been known to deliver his amps, if you are not too far away. Packaging of the heavy Claytons is excellent, as it appears to be for the McIntosh also. At this price level, it would be nice to hear them first, but you mentioned you are purchasing used so that may not be an option.