Since I am unfamiliar with the JM-lab speakers (I thought they were known as Focal nowadays), I cannot compare the two.
I have owned the Ohm Walsh 2000s since late 2009. You can read my initial review of these speakers in the Audiogon review section. I have also commented on them at length in this huge thread:
A lot of the criticisms I have had of these speakers have turned out to be upstream issues with electronics and wires. Eight years on,I am enjoying them now more than ever. I think they may be my last pair of speakers. They are wonderful with a very wide range of musical genres, including the ones you listed.
They do like a lot of power, although they will sound good with less wattage (you can even try them with your NAD - you never know). I run mine with a pair of powered subs, so the 150 watt-per-channel amp I use is plenty (Odyssey Audio HT3 with cap upgrade - the 2-channel version starts at $1500). But I did try out a pair of 500 watt class D monoblocks, and there wasn't much of a difference that I could hear. Other owners of these speakers have reported that 300 watts per channel or more will bring out the best in these speakers, but I am loving the sound I have now. As for tube amps, as long as they are a solid 100 watts per channel or more, it could work. I would definitely call John Strohbeen, Ohm's designer and owner. He is accessible by phone (less so by email), and will give you honest, helpful advice on getting the most from his designs in your particular room.
No speaker is for everyone, but the Ohm Walsh 2000s are definitely for me. I could not be happier. But whether they are for you or not depends on your ears and taste.
BTW, I also run a modified Beresford DAC (by K-Works, called the "Superberry DAC").