his first post indicates he was looking at the dart separates; NHB-18NS pre and 108 stereo amplifier. then got feedback that the dart stereo 108 'might not' give him the "power with finesse" that he prefers on his ascendo's. so also considering the other 2 brands. would he also add preamps from those other brands? it's a question.
i'll agree with Keith and Frantz that those particular other amplifiers have little if anything to offer in terms of power and authority over the 108 dart on the 91db, 8 ohm Ascendo's. and that he already knows about the darTZeel character. since 5 years ago with the SCNP upgrade the NHB-108 has been quite a bit more authoritative with moderately tough loads.....which 91db, 8 ohm ascendo is not. and as far as finesse, it's right there with anything, anywhere.
and the new NHB-18NS pre brings a level of it's own finesse and dynamic authority as well as a world class phono stage to boot.