Zokes I'm just airing my opinion as you are yours.. hopefully you won't interpret it as some sort of war/crusade
If one is just starting out, they'd probably be better spending the money on the glass. Having an expensive body but average lenses seems a bit pointless. Not saying you have this.
Forgetting low light for a minute. The OP's question was open ended. Should I buy a prime?
A prime will almost certainly beat the zoom at the same focal length which I think is some of what Molgrips might be getting at as well as other things. Its madness to think someone would be always shooting at the widest aperture all the time. Not many lenses are sharpest at their largest aperture.
The cleaness of ISO is a property of a given camera. These cameras are like computers. Generally speaking a better one will be out in the next year or two with some ISO gain. You might still have the same glass. So the benefit of the new body might not be fully realised because the glass was never invested in.
Throw in IS, which is usually only found on slower zooms, and you will get much better low light results than if you didn't have high ISO ability, or IS, but did have a prime.
Again life exists beyond the realms of Canon and Nikon. Stabilisation can be found in the body and therefore applicable to any lens that fits the given mount. So this stabilisation premium per lens is not always a problem - it depends on what system you run. These other brands include Pentax/Sony/Olympus to name a few which all have in-body stabilisation systems...
The OP has Nikon so yeah he will have to consider that. Other people might not though.
For the record I did have a Canon Powershot compact many moons ago and I've also owned Olympus and Panasonic cameras in the past.
And now I fly off on another rant (I'm sure in another life I was destined to work for Pentax marketing - which I believe are criminally underrated and have been badly marketed)
Many will think I'm mad (probably some truth in that). I changed to Pentax for tank like build quality, in body stabilisation, range of great primes (new and legacy - four of six lenses I own are primes) and also various weather resistant lenses that allow shooting in adverse conditions as this US marine demonstrates in Afghanistan (his blog is very interesting regardless of what camera brand you shoot with):
Many people on this forum would not limit themselves to two brands shopping for considering a bike or bike components...
What was the question again, OP - Yeah go get yourself a prime!
and forget about everything and enjoy whilst the rest of us squabble