Yes. John Hillig at Musical Concepts does a wonderful mod of this amp.
I had the amp with the modifications. I think there is one newer one now. The amp was warmer versus the typical SS sounding amp in the lower price range but SS none the less. The amp produced deep bass that shook my house. It was smooth sounding also. I bought mine used for around $1000 years ago. While is was a good amp it was not in the same league as the Counterpoint SA-220s that I owned which had better overall sound, mids, highs but did not have the deep bass drive of the modified Hafler. I never was able to compare the modified one versus the stock one. I now do all my own modifications and could do your also if you wanted to.
What John does is not really a mod. He replaces the Hafler boards with his own. Not a bad move, but you are really making it a different amplifier. If you are up to it, there are plenty of part replacements that make a massive difference that will keep the original Hafler flavor. I have attached a cheap kit from Fleabay that would make a huge difference in a DH 220.
1) Replace small signal cap and small dielectric cap
Replace small signal cap with polypropylene cap, replace small dielectric cap with Nichicon audio grade cap
2) Power supply mod and small cap
replacement small signal cap with polypropylene cap, replace small dielectric cap with Nichicon audio grade cap . Replace with Nichicon Audio grade big cap and replace rectifier with Hexfred rectifier.
I can change the amp to sound however you prefer depending on caps and resistors. They all have a sound. You have to realize that this is a basic amp and mods can make anything better if you know what you are doing but I cannot make the amp a world beater just better. I bought the amp with Johns modifications because he said it would be tube like sounding. It was not tube like sounding.
Send me a message direct and we can discuss more.