If you got the NAD C298 then the Benchmark LA4 seems like the natural fit for me. I say this because the Purifi amps are described as being very similarly to the Benchmark AHB2. The LA4 and AHB2 are what I use in one system.
I just bought and returned the NAD M22 V2 which I selected over the NAD C298 because I wanted something that did not sound like the AHB2. I returned the NAD because the AutoStart feature was problematic with my 2-amp setup on my CODA 07x preamp. I was happy with the sound of the NAD M22 V2 for its intended purpose, I just could not disable the AutoStart.
If my similar sounding assumption of the C298 and AHB2 is correct, then a CODA 07x preamp would likely be great the C298. I love the combo of CODA and Benchmark preamps and amps (all combos). The 07x preamp is very different from the LA4. It will add some tuby sound to the mix and it is not dead silent like the LA4. My fav is the LA4, but the 07x could be better with the C298 if you like a bit of warmth.