Talk to me about your progression in amps... were you always bi-amping? I have a pair of Polk LSi25's that is a semi similar design as your NHT's. I recently went from a 4 channel Adcom giving 90W/ch, and upgrading to a 2 channel Rotel giving 220W/ch. My Polk's are low efficiency 4 ohm speakers, the extra watts proved a bigger upgrade over bi-amping.
Curious to hear what you had and thoughts on changes along the way!