It depends on how the old DVD's audio connected to the surround system. 5.1 and 7.1 analog outs went away from Blu-Ray players built after Feb 2012 because the Hollywood studios wanted that and mandatory Cinavia copy protection. They disappeared from DVD players around that time too because those became too cheap to include such premium features.
If the old DVD player connected via digital: coaxial or optical S/PDIF, then nothing has changed.
If it's an all-in-one system where everything is in one box then all connections are internal and it's junk now.