The NSMT Model 50 Jamaica is closest to the Zu Omen II, pricewise. Interestingly, the transmission-line NSMT is quoted as "not needing a subwoofer" while being spec'd to 42 Hz bass response, whereas Zu Omen II goes to 38Hz with useful response a little lower. Both companies put their main drivers in a direct connection with the tweeters on a high-pass filter. The difference is that Zu's full range driver is driving sound up into the 10-12kHz range, at which point the harmonic-completion duties are handed off to the supertweeter. The NSMT hands off driver duties in the mid-4kHz range and is a ported speaker with some peak notes emphasis. The Zu is neither sealed nor ported -- it uses their Griewe driver-to-room acoustic impedance matching scheme that is remarkably and passively adaptive to room considerations.
Both companies have some similar convictions (avoid crossovers) and some differences (Zu pushes the handoff between main driver and supertween above 90% of the music content, and avoids ports). The woof-tweet-woof arrangement of the NSMT tower limits floor and ceiling effects like Zu's more expensive Omen Def Supreme, but the Zu brings more dynamic, tonal and behavior unity to the party, and a bit deeper, faster, more tuneful and toneful bass. I'd go for the Zu Omen II for its tonal, transient and dynamic unity but the NSMT is in the crossoverless realm with more than decent chances of success for you.
Phil