Some components too old now?

Hmm. Thanks gdnrbob - really interesting.
Reading that thread, and over-summarising again, it seems as though a really good 90’s DAC (like the Aragon) will still sound as good as a decent modern one, but the difference is a modern one will have far more functionality. 
Is that the way you read it?

I dont know those specific components well, but in general i agree with Eric and others.  The preamp is probably fine the DAC likely can be vastly bettered ( and Schiit is a great place to start). I can't speak for the Marantz, but bear in mind that SPDIF is NOT, repeat NOT, a purely digital signal - no time to go into why, by you need a low jitter output.
A new DAC with USB and/or network in also lets you move toward the future, which is streaming.
I am constantly amazed that stuff that was great 30 years ago is often still great. But not digital.
G

Oh, one interesting caveat.  We had a group listn to two old DACs - that were eye -popping whne they came out 20-25 years ago, and one new one, a schiit BiFrost Multibit.  Long story short the 1994 Theta DSPro hung on with the Schiit - and was generally a little weightier.  Still a top notch, musical product. Note Mike designed both.
G

I’m using an optical connection between the CD and Aragon DAC. I must have discovered long ago that this gave me the best sound. Is USB any better...?

PS I don’t think I’ll ever use streaming or HDD so that’s not a consideration. I’m primarily vinyl, and CDs are so cheap these days second hand.