I have restored a Marantz PM94 and have recently purchased a pair of Von Schweikert VR4.5 speakers, am using Apple Music through my iPhone. What would be recommended to improve the sounds? Also have a restored Sansui 9090DB with stacked Advent speakers. Just read on the forum about the value of preamps and wondering if I should be looking at a tube preamp to add to my systems? Am retired so not looking to spend big bucks. Thanks in advance for suggestions.
Your marantz is a integrated amp and already came with a preamp.
To make the sound better, you can get an affordable full function streamer+DAC like the Wiim pro plus for 200 bucks.
https://www.crutchfield.com/p_399WIIMPPL/WiiM-Pro-Plus.html
If you are operating on a restricted wallet, look at the "Cheap Audio Man" YT channel. The guy generally talks about affordable/ relatively higher value gear.