Can old equip work with today's technology

Assuming you have cable or satellite, you should be able to get audio from the receiver to your stereo.

On a newer TV that does not have any analog RCA outputs you need to get a Digital to Analog Converter box. Most TV's will output PCM through there digital output.
However some TV's only output Dolby Digital in which case the DAC needs to be able to decode dolby digital. Your TV's owners manual should tell you if it outputs PCM or Dolby digital.

If you search Digital to Analog Converters you will find plenty of choices.

I am sure the music you would get from an "old fashion" source like a TV or a tuner would sound pretty good, isn't there some inexpensive computer you can find with internet connectivity. If not do what we always did find a tuner -which BTW are selling for close to nothing- and play a good station through your high end gear it will sound pretty good.
A little off the track of this thread. I was able to buy excellent digital Sansui Tuners for really next to nothing, models like the t-60. The more expensive ones were all analog but not tube like the TU-919, I own a TU 717 amongst others they sound great playing throughj modern gear.

There are plenty of satellite radio stations to listen to. I listen to Sky FM which has a multitude of different music to try. I bought a cable that connects from the jack on my smart phone which connects to the AUX. on my preamp. Sky FM is free, but I pay $5 a month for the higher grade signal. I'm listening to a wide variety of music now, and it sounds excellent!