NAD may have made their name with budget products, but the M2 is not and does not sound like a budget product, IMO. It was an all-out assault on the reasonably-priced high-end, using a new technology that has many advantages. It's not your grandfather's digital amp.
The M2 has received near universal praise from professional reviewers (TAS, Stereophile, Hifi News, 6Moons) as punching way above it's price class. The trickle down has the 390DD performing similarly, but with less power and a cheaper price tag (and maybe somewhat smoother/ softer in the highs). The M2 will have no problem driving your SF speakers and can be found used for just a little over your budget.
I use an M2 in a system with $35K speakers, and find it a good match. Like many SF designs, these speakers (Peak Consults) are elegant and slightly warm through the mids and a little soft on top. The M2 replaced a well regarded $4K amp and gave me more of everything I value. It's quiet, dynamic, neutral while allowing for good tone, and controls bass lines with an iron fist. No, it doesn't sound like a tube amp, but it should be kept in mind that these NADs are (true) digital amps taking a digital input, and the volume control does not lose bits or affect the sound quality in any way I can determine.
Whether it will float your boat (or anyone's) or match with your speakers in the way you like is a different matter. But I'd be hard pressed to recommend a similarly priced integrated to try that obviously betters it. Maybe the Modwright or Pass or Hegel or Ayre will give you a take you like better, and if you already have a really good digital set up, or want to spin vinyl, the NAD may not be your best option. But otherwise, I'd consider giving it a spin.
And FWIW, I've had no problems with mine....