I would say it depends on your receiver. The NHT's tend to require a little more juice than the Axioms. Tonally, they are very, very, close. The full range T5 and T6s certainly offer more adjustablity than the Axioms (with the X1 crossover), but your room is a large enough size that it shouldn't be an issue. The NHT offers an identical center to the left and rights: I was not thrilled with the VP150 center. I found it had serious tonal changes as you moved off-axis, changes I do not hear with the M5. BTW, in your size room the T5/M5 should be plenty.
