I think it depends what you're looking for. NAD, HK, and Marantz all offer robust power supplies (prob in that order). In terms of sound quality, none are slouches. IMO NAD focusing almost entirely on music makes them sound wonderful, HK is warm and dark and inviting, Marantz is a very neutral sound. Of course, the sound of receivers isn't nearly as different as those of speakers.
Onkyo I've never liked very much, just a personal preference. I've always felt they cater more towards movies and home theater than music. They do well with music, but in my opinion, the other 3 do much better.
Go listen, feel them, use them and decide for yourself which you like best!