stock DNA-225 is an excellent amp. There is a review of it in stereophile where the reviewer compares it to a fully modded DNA-1. Look at the review. The comments on DNA-225 in that reviw are pretty accurate. Some people say DNA-125 and 225 sound the same, but I haven't found it to be the case. 225 is more refined. Stock 225 is very nicely balanced. It was never bright or harsh sounding in my system. Very easy to listen to with excellent dynamics and good bass extension. The sound of it will depend on what you feed it with and your speakers. DNA-225 has very smooth highs. Smoother than DNA-125. I had the older 0.5 Deluxe as well and loved the highs of that amp. Stock 225 matches it on sweetness but at the same time it is more detailed and resolving without being bright.
Hope this helps.
Hope this helps.