Upgrading/changing Speakers with late 70's McIntosh System?

Would appreciate advice on upgrading speakers from anyone familiar with late 70's McIntosh Equipment. Current system:  MC 2125 amp, C28 Preamp, MQ 101 Env. Equalizer,  Mac XR 5 loudspeakers (4 way--- 12 inch woofer, 8 inch lower mid range, one 1/2 inch upper mid, two 2 5/8 inch tweeters).  Paired with REL S 510 subwoofer, and Bluesound Node X streamer.

The simple question is whether it is a mistake to try and combine my older Mac equipment with new speakers, such as a Sonus Faber Olympica Nova iii (v.?) or SF Maxima Amateur or perhaps Sabrina X?  Is there a synergy or compatibility that would be lost that I currently have with my Mac XR 5 speakers?  I do very much love my current system, particularly for the presence and realism in acoustic music and voice,  but would like a bit more detail than my Mac speakers are giving me, which I do hear in newer speakers.

I know the Mac XR 5's were never highly reviewed, but they emit a fullness and lifelike presentation of voices particularly, in my current room, that I find wanting in some demo's I have done in dealer showrooms with higher end and newer Mac equipment paired with the Sonus Faber Olympica Nova III, or the original Sabrinas.  Not saying either of those are not great speakers-- in fact I want to like them!  

What I lack, and am looking for, if possible, is to retain that warmth and fullness and realism I find with my current speakers but with some of the detail that I know I am missing.  Or perhaps for a compromise of the two if they are somewhat mutually exclusive.

In the end I think it come to auditioning a speaker in my room.  I did do this with the original Wilson Sabrina- but the dealer had problems with the streamer and some other settings, and agreed it was best not to change to the Wilson's in that particular case.

Anyway, I'd appreciate anyone's thoughts.  I would add, if its helpful to anyone, that the REL Subwoofer addition was a huge upgrade and well worth the dollars.  They disappear and simply give a tight clean base that reinforces the entire range of the speakers.  Also would add that finding the right room for the speakers made an equally huge improvement, or perhaps even more so.

Thank you in advance.  This is such a great hobby and lasts a life time, as my 40 year old plus equipment is a testimony to.  (Bonus question:  why were we taught not to end a sentence with a preposition?)