I'm not familiar with either of those mods, but have owned a DH220 and DH500. While both are powerful and stable amps, they're not among the most transparent or musical amps I've owned, so I'd definitely consider pursuing some possible upgrades while you're inside of it. IIRC, years ago I think Musical Concepts and VanAlstine had some well regarded mods for those amps.
Good luck, and please post an update regardless of which direction you choose.