Can I use a Bluesound Node 2i as a Preamp?


I just recently purchased a Bluesound Node 2i to use with my CXA80 integrated amp. However in future  I’m looking at upgrading to a high end power amplifier. As I’ve had the CXA80 for years I want to try a few different DAC’s etc. So in future I’m looking at buying a high end power amp I can plug some RCA cables into and use some different bits of kit. 
Whilst I was on the phone to the guy from the audio store, whilst purchasing the Node 2i I asked about connecting the Node 2i to an NAD M22 as an example. He warned me not to do that for too long, as I’d need a proper Preamp, he was warning me that the Node 2i is not a Preamp. Fair enough but I am a bit confused, what does a Preamp have that the Node 2i does not? How do you define what a Preamp is then? What is the risk of connecting a Node 2i to a M22 directly via RCA? Or is this just a traditional thing that you need a big preamplifier for a big amplifier? I can’t figure out what the reasoning is. Is this to do with grounding of the preamp? or something else? Any feedback would be appreciated. 
andyboom
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The Ayre Codex was a good suggestion, though the Node 2i doesn't have USB out, so you'll be forced to use Optical from said Node 2i to Codex.  Probably not the best, but it will work.