After using the Dreadnaught on and off for a few years, I can say I would have never called them bright. It is, if anything, slightly laid back. (It sounds closed in until they warm up a while.) I found it to deliver sound in a very convincing way once warmed up. My major complaint was a little conjestion in the mids compared to my Ayre V5xe.
I would look at associated components including cables. You can't fault an amp for delivering what it is fed (Which I think is the case.) I have never owned the Model 8's but have heard them numerous times and I always considered them a touch bright to begin with. A neutral system is going to reveal some bright recordings because they are a bunch out there. My point is, in your system, it may be bright but I really don't think it is the amps fault.
I would look at associated components including cables. You can't fault an amp for delivering what it is fed (Which I think is the case.) I have never owned the Model 8's but have heard them numerous times and I always considered them a touch bright to begin with. A neutral system is going to reveal some bright recordings because they are a bunch out there. My point is, in your system, it may be bright but I really don't think it is the amps fault.