What next?

Node X is kind of spendy, if you don't need the added features, pick up a used Node 2i

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.

Budget $1-2,000 am ok with used if reviews show it worthwhile. 

Schiit Freya + (I use the original version) and maybe a Bifrost 2/64...both sound first class and are somewhat "el-cheapo a mundo."

You’re where I was 6 years ago, great speakers, crappy front end.  Buy a used Innuos Zen Mk3 and a decent DAC like a used Schiit Yggy.  They’ll make you happy!