Preamp to Pair with NAD M23

The Benchmark may be a good candidate.  The other thing to consider is moving up the Bryston line.  Here’s a nice BP26 at a good price — it doesn’t have the phono section but you could either use the one in the 11b or get a better separate phono stage, which is what I’d do as it’s an important component.

https://www.audiogon.com/listings/lisb6ebf-bryston-bp-26-17-silver-mm-phono-excellent-solid-state

 I had a BP6 for years and it was the proverbial “straight wire with gain” component that produced a silent backdrop from which images just popped within an expansive 3D stage — it was a poster child for utter transparency.  James Tanner told me the BP6’s topology is near identical to the BP26 with the major difference being the 26’s balanced connections and separate power supply. I’d have to assume over the past 25-30 years Bryston has made some significant improvements so this might be worth considering if you just want more of what you already have. 

For my money, you want color to go with those amps.  Maybe time for a tube pre. :)

@erik_squires makes an excellent point.  There are some neutral tube preamps that may be a big improvement in several ways over what you have now.  I’d recommend taking a look at the Linear Tube Audio MZ2.  I actually bought this to replace my beloved BP6 if that tells you anything although I unfortunately haven’t gotten to listen to it yet.  Here’s a nice used one at a 42% discount from its current price and comes with the all-important linear power supply upgrade, and if it doesn’t blow you away you can just turn around and sell it for little/no loss — well worth the risk IMHO.  The tubes in this thing last a looooong time and are cheap to replace, so don’t let that dissuade you, and as a bonus it’s a first-rate headphone amp if you ever swing that way.

https://www.usaudiomart.com/details/650017308-linear-tube-audio-micro-zotl-mz-2/

I tend to be a tube fan, especially in a preamp.  In addition to the potential for stellar clarity, you can roll tubes to tailor the sound to your liking,

Thanks everyone for the suggestions.  I went with the Linear Tube MZ2 after checking out some reviews.  I'll report back on the sound when it gets here.