Wow - that's a lotta feedback. Thanks, all. Let me start by saying I prefer the M2 in nearly every way over the Creek. While I could still return it, I doubt that I will. The top-end and midrange are noticeably more spacious and detailed. The soundstage is certainly wider (though perhaps not deeper). Transients are much more obvious - you can really hear the pluck of a string with this thing! (sorry) There's more music there, or the pacing's better, or... something - I just want to sit and listen, where I'd find myself getting a little bored with the Creek in the mix. You know what's really cool? Space. In music where there's lots of space (I'm mostly a jazz guy), instruments are set against an utterly black background. I've never heard anything like it, never knew I wanted it, and it's awesome. In short, The M2 addresses many of the "problems" I was hoping to solve in purchasing a new amplifier - and gives me some extras I didn't even know I "needed". I like it - a lot. I just wasn't expecting a perceived bass deficiency, I guess because a) my speakers are pretty sensitive, b) when I heard the amp prior to purchasing, it certainly did not seem bass-shy to me, and c) reviewers had specifically commented on the quality of its bass.
I burned-in the amp for about a hundred hours before paying much attention to its sound - though it may be that it could use more. I'm still running it continuously, so we'll see if the bass opens up some as a result.
I run Pangea power cables for all my equipment. The one I use for my Creek made a huge difference. I never bothered with the stock cable on the NAD. Maybe changing my power cable will help here - hadn't thought of that.
I've had the Creek for quite a few years, and am probably used to its sound. Synergy is the reason I own the speakers I own. When I decided to upgrade from my Totem Acoustics a few years ago, I didn't want to go upgrading my amp as well. I chose the speakers that sounded best to me with the Creek: Paradigm Reference Studio 60v5's. These were not my favorite speakers, but the Aerials I fell in love with lost their magic with the Creek - and I did (and do) really like the Paradigms.
To Mezmo and Winoguy's point, I do kinda think I need to give myself more time to settle in with the M2. FWIW, I spent a LOT of time on speaker placement, chair placement, room treatments, even equipment placement (sidewall!) when I built out my listening room (I'm one of those Jim Smith disciples who believes the room and positioning are exceptionally important factors - and this is where I've spent a healthy amount of resources, while allowing myself to purchase what some might call "budget" equipment (a la Creek and Paradigm), instead of, perhaps, vica verca). So my biases tend to lead me towards fixing problems by optimizing the room first - then looking at everything else.
It's possible the bass coming off the Creek has been a little bloated all along. I "voiced" my (Creek) system using a combination of headphones, room treatments and RTA to get pretty flat in-room response from the Paradigms. BUT I never heard the kind of texture through the Creek that I do through the NAD. The bass is just (seemingly)... bigger through the Creek. It may not be better. Hmmm... could it all be in my head? Could be, could be.
Like Mapman, I'm moving from a Class A to a Class D. More and more, it's sounding to me like I need to let the M2 burn-in some more, sit and listen some more, and then potentially suck it up and go through the whole room optimization process again. I hadn't really anticipated that, but like many said, it's part of the "fun" right? Then perhaps start looking at my cables. Then possibly optimize again. Rinse, repeat!
Thanks everyone.
