I had the DNA-225 for many years and thought they were very good. I moved to the Pass Labs XA60.5, XA100.5 and then XA100.8. They are markedly better than the DNA-225, specially in imagining and purity of mid range. With that said, if you have power hungry speakers, I wouldn't recommend the XA series unless you are willing to buy one of the big boys. Even the XA100s with power hungry magnepans can be pressed. They don't leave class A but don't produce high level SPLs.
Recommendation for Improvement over McCormack DNA-225
I currently have a McCormack DNA 225 mated with a VTL 2.5 and Line Magnetic 502 DAC powering my Salk Veracity HT3's. I think it sounds really nice but can definitely have some top end harshness, especially at the volumes I like to listen to. I consider the Salk's are fairly power hungry in the low end (as confirmed with Jim Salk), can anyone recommend a SS amp with as much grunt as the McCormack in the range of 2K plus or minus. Sure I would like a Pass or Ayre, but those are way above my price bracket. I've tried Bel Canto Ref1000 mono's and Van Alstine. The DNA had a better mid range presentation and better bottom end than both, no comparison. Any other recommendations shy of the DNA 500, which again is over my price range.