What is the rest of your system? I know that the Hafler can be modified with excellent sounding results. You just have to determine if it is worth it to you. Some of the Class D amps are very nice sounding for not a lot of money.
Anthem gear is nice, you might want to look at the Marantz PM8004 as well. A ton of stuff to choose from around that price range.
Would the newer stuff out shine the old, not always. Let your ears be the judge. Keep in mind other features that may be important to you, headphone output, A/B speakers and such. Built in dac, remote control etc. Even the seemingly can I read the writing on the unit. All will add to your enjoyment of your new gear. Post how you make out. Happy hunting.
Before you make any comparisons: Your DH-500 is over 25 years old. Replacing the electrolytic power supply filter caps and the two electrolytic input(C1)caps(here with polypropylenes), will make a major difference in it's presentation. These simple to perform acts will go a long way toward leveling the playing field.