I use a Windows PC for my Roon Core, my 2 streamer DAC is Teac NT 505 and Auralic Altair.
I am looking to upgrade to lifetime membership and Roon Nucleus or Nucleus+. Do I need the Plus?
Thanks
(All my connections are Ethernet and I never any problem with streaming or no connection. I have Ethernet everywhere my music streams to.)
It is based on how big your roon library is and how many zones you wish to stream to, it is shown here on the https://roonlabs.com/nucleus.html
To give yourself a sense of comfort with their respective capabilities, you may want to look at this thread: List Your NUC Capabilities Here
Simon Pepper and I did a comparison of an i3-based NUC vs the i7. The i3 is very, very capable. The regular Nucleus has that processor.
So, unless you have very demanding situations, or are a person who wants to feel comfortable having the most powerful version (I stand guilty), the Nucleus will probably be perfectly fine. The money you save will pay for your lifetime Roon membership! 
There was a time when a NUC ROCK was included in the discussion. I paid for my lifetime subscription and satisfied my “need for speed” (i7) AND took my wife to dinner.
A NUC ROCK is easy and is worth your time.
There are two criteria for deciding between i3 and i7.
The first criterium is the size of your library: huge library choose for i7 (see info about NUC on the website of Roon)
The second criterium is: do you want to resample your music to higher frequency or to DSD. If so, choose i7. Resampling is processor intensive. Fortunately the Nucleus(+) provides more than sufficient cooling without making use of a fan.
My choice has been easier: I had to choose between a nuc i3 and a nuc i7. In case you will consider between both: choose the nuc i7 and invest also in an Akasa Turing housing for passive cooling in order to prevent noise from the fan and to keep the temperature of the processor well below 60 degrees celcius.
Lots of good advice already. As for me, I chose the Nucleus. I have fewer than 3,000 albums (about 39,000 tracks) and can’t imagine reaching 10,000 albums (or 100,000 tracks), the point at which a Nucleus+ is recommended. I do some up-sampling but never strain the capabilities of the processor. I also operate in one zone at a time but you can operate up to six simultaneous zones with the base version. Finally, response is snappy with no lag. So, for me, the base product was the answer and I have been totally satisfied.
I have been running ROON for the past 3 years on a 2015 iMac w/ Fusion HD with FLAC files stored on an external HD. Audio player/streamer is a Linn Klimax DS which connects via UPnP - in other words it would not benefit from being able to connect directly to the NUCLEUS (as it cannot connect in this way)
Recently I have been contemplating the purchase of a NUCLEUS+ however it has come to my notice that we need to purchase a new iMac. The new iMac will be a current 2019 model however it will be spec’d with a SSD hard drive. At this point the addition of a SSD and a current 8th generation i7 Intel processor should provide all ROON needs to run on the iMac.
Would I gain ANYTHING by the purchase of a NUCLEUS + at this point? Me thinks not.
PS the iMAC resides in the kitchen and is strictly used for some light internet surfing. The majority of the time it sits idle.
Maybe. Maybe not. Two points: 1) I like having my Nucleus on 24/7 so I may access music without firing up a PC, which I had used prior to buying the Nucleus. Since your Mac will reside in your kitchen, perhaps that’s not a big deal. 2) More importantly, the Nucleus runs a stripped-down version of Linux, which is totally dedicated to playing music. I found a sonic difference between my Win10 PC as core and the Nucleus as core. Your mileage may vary! 
Thanks for the reply.
You are correct in that my kitchen iMac will be powered on 24/7 and will only be sued for random internet surfing
As to a sonic difference - I would think perhaps if one is connecting their DAC via USB in which case I can see the advantages of a NUCLEUS. In my case my Linn Klimax DS connects via UPnP - which in my opinion negates any advantage which the NUCLEUS might have?
Just curious - if the Linn Klimax DS only connects via UPnP, then how does Roon talk to it in your setup?
Since Linn remains committed to Open Source protocol they will not embrace RAAT.
Linn and ROON worked together on a protocol which enabled Linn devices to be Roon capable - but not Roon Ready.
Implemented in Roon 1.5 in May 2018
Ah - so that’s what the “Subnet for Linn Streaming” option in Settings/Setup is for… Not having any Linn equipment, I’ve never paid it any attention. Thanks.
I can only speak to the difference between my Win10 PC and the Nucleus, in which the latter stood out in SQ. I would imagine the same would hold of a Mac but can’t be sure. As to other setups and the difference a Nucleus might make, I have no experience. Hope all works out for you!
I use a MAC Mini that I modified to run on 12VDC. The beauty of that is in my 2012 Mini I can install any HD I want…I use a SSD for Music and a HDD for Back-Up all inside the Mini…really fast and quiet…I run the USB outlet to a DDC that coverts the usb signal to a AES out. My (Audiobyte Hydra Z) DDC runs on 5VDC. If/when this gear craps out, I’d probably look at the Nucleus +.