I was always quite surprised at just how capable was the AV2 as a pre-amp. My AV2 had to stand in for a NAC552 for a few months as my own NAC552 that had just been built kept being sold by Doug before I could nab it from the factory (one of the disadvantages of being Export Sales Manager was that if I was away then I couldn’t really moan about it ;). However, I would expect a Supernait 2 or 3 to be appreciably superior to an AV2 and NAP150 - by how much, I couldn’t say without a comparison. The good news though is that the CDI is still a cracking good source and should partner the SNs well, so long as it’s still working OK. The Bluesound Node maybe not so well - it could be exposed by even better amplification, but then there are Naim’s own network players to audition here…
I have both an av2 and a SuperNait. The av2 is good but not magic as a normal stereo preamp. I find it especially good for what it is designed: an av-preamp. It sorts out all earthing / noise complexities and somehow it just sounds fantastic in movies. Don’t know what it is really but when I use another Naim amp, I get ground hums (can be solved with a bit extra wire) and it does not sound so magic & has no rear channels.
Can’t you keep the av2 for av purposes, use the SuperNait for front / stereo loudspeakers in av bypass mode? That will give best of both. It’s described in the av2 manual if I remember it correctly.
I’d suggest you’d likely want to try out a SN3 (without a HiCap DR) vs the SN2 + HiCap DR.
I personally found the SN3 more than capable of standing on it’s own and doing what a SN2 only really seems capable of with a HiCap DR.
Both decent integrated amps tbh but do try those combos if you can before making a commitment, enjoy!