Altough you will get greater gains from upgrading the NAC (first) you will gain from replacing the 150 with a 200. The thing I thought most noticeable was greater detail and "texture" in the bass. That was with a CDX2/112/FC2.
So it depends on the context in which you are asking, if you are being opportunistic and have a good opportunity for a deal on a pre-loved or ex-dem 200, then I would be very surprised if you regret taking the opportunity. In my case I was holding out with the 112 until Naim modernised the pre-amp range. Unfortunately, my patience was ultimately a little shorter than the development cycle for the N272. Same story with the Uniti-serve and UnitiCore.
When it comes to power amps, they will always be with us. The question (with ever improving class D) is whether you should have them built in to your speakers. If your answer to that choice is a firm no then you have nothing to lose from a 200. There is a lot less certainty upstream.
Olly
