Nuprime vs preamp rebuild.

Had previously queried community re value of upgrading dac.  In brief I have an AR SP-3 preamp, Prima Luna HP amp, Magnepan 1.7 speakers.  The dac is from HRT and is (I believe) their original model.  Good quality interconnects and power cord.  Up to this point, have been using Spotify Premium as streaming source.  One respondent recommended getting the SP-3 up to speed.  Last service is long ago, though usage has been light.  The price of a rebuild done by AR is about 3K, all costs considered.  Another respondent advised purchasing a Nuprime 10 which would cover both the preamp and dac issues.  Would very much appreciate any thoughts re these options.  Thanks
I haven't listened to the AR SP-3 so no comment there but if by the the original HRT you mean the HRT music streamer that is not asynchronous then yes you can do a lot better. I own one and now own a nuprime DAC10. The difference just in dac quality is substantial. Even if you don't get the nuprime the HRT could be improved upon with some newer and very affordable Dac's. The nuprime is an excellent line pre as well. As good as your AR? No idea. 

Is Spotify premium 16/44 cd quality? If not then you might want to try tidal Hi-Fi to see if you notice a difference. 
Spotify premium is 320 kbps. CD and Tidal are 1411 kbps.  Unfortunately capacitors and other parts age with time regardless of use to some degree 
Joe gator and jl35 thank you both very much.  I realize that my question borders on the ridiculous.  I think it is highly unlikely that anyone in this community could meaningfully comment on a rebuilt SP-3 vs. the Nuprime.  At this point cost becomes a real consideration.  To get the rebuild and a high quality dac would run > $4K and the Nuprime would be less than half the amount.  I can afford to go the high cost route, but I am clueless as to whether it might result in better sound.  I very much enjoy and appreciate a good music system, but I am certainly not a cost be damned fanatic.  I think my next move will be to contact the Nuprime distributor in N CA.  And I definitely plan to give Tidal a shot.  Reading the blogs, it is quite interesting how widely opinions vary re Spotify vs Tidal.  About half the people feel that Tidal is significantly better, while the other half feel that Tidal is marginally better at best.  
As is said often, let your ears decide. I think tidal gives 1 month trials. If you decide you like it, take my advice and don't favorite everything you like, build playlists or just favorite the artist and not each individual album. I have found so much amazing music that I'd never have found otherwise and began "favoriting" it all. Tidal runs a lot slower this way, I've not noticed any loss in sound quality but the desk top version is a pain to scroll through. I've noticed no such issues w/ my iPhone though so it may just be my old laptop. 
Thanks for the above.  Given the age of my SP-3, the Nuprime preamp may do just as well, perhaps better, and of course the dac upgrade should be substantial.
I actually went from the HRT to the Halide DAC to the Nuprime. Each jump was very positive. I think as far as the DAC goes you will be impressed. Try to find a dealer that offers a return policy. 
Keep the SP3! It is a TRUE classic and worth some restoration! But don't send it to Audio Research - they will charge way too much! Even in its present state it can compete with today's top preamps! Just changing the power supply caps and adding a set of NOS tubes will be worthwhile! I own an SP6 (1976) - and speak from experience! 
Dear roberjerman—thank you very much.  I was aware of the status of the SP-3 and had no intention of parting with it.  I spoke with AR directly and got the name of a certified technician in my area whom they highly recommended.  Spoke with the latter who told me that while he would love to have my business, he felt I would get more for my money working with AR directly.  In a full rebuild, AR installs a new circuit board (I think that’s the term) which no one else can provide, and I came away with the impression that this was an important difference.  I actually never requested an estimate from the local technician what his services (parts included) might cost.  I was thinking that I would set the SP3 aside and that at some point in the future I would proceed with the full rebuild.   This leaves me with two questions for you or anyone else who cares to comment.  How do you think the preamp function of the Nuprime would compare with that of the SP-3?  Is there a big drop off or is the the difference a more modest one?  I still plan to upgrade the dac with budget around $1K.  Any recommendations?   Thanks in advance to you or anyone else who cares to comment!
I'll just reiterate that I've not heard the AR not have I ever had an AR in my system. Prior to owning the nuprime I had a belles 22a tube Preamp with the Halide dac. I also spin vinyl so the analog line pre function was very important to me. When I bought the nuprime it was going to have to be 1) an improvement in DAC quality... it was 2) and be at least the equal of the belles overall in sound quality... it was and though I didn't do a lot of a/b comparisons I think it was better. 

Does es that mean it's better than your AR? No. It does however mean that it's no slouch, at least to my ears. 
Dear Joe— thanks for your last remarks; they were very helpful.   I phrased my question rather poorly, as an a vs b comparison, not a realistic approach at all.    What I really needed to know was whether those who used this unit were pleased with its performance, and I would say that you have made a strong endorsement.  I am actually in the process of ordering it at this time.  js
I hope I helped and you like the nuprime, it will be in my system for a long time. 

Btw, there is a guy who mods nuprime with their blessing. Most say it's worth it but I haven't tried it yet, focusing on my analog front in for now. does the mods