Well, I actually think that the Marantz-PSB combination does very well for vocal-based music. It is not exactly neutral. But it does not set your nerves in a jangle.
In the 25K budget range, the Image B25s are special speakers. I would be very surprised if the Usher S520 beats the Image B25s. I have still not had a chance to listen to the Ushers though.
Another interesting speaker choice for you would be the EPOS M5i. It is a very highly recommended speaker. Fatigue free listening and excellent performance on vocals are its strong suit. Do see if you can audition this one. From experience I can confirm that they do indeed do well with a Marantz.
On a side note, Marantz is the amplifier brand for Jazz music. The way it draws out saxophone sounds is superior to many other brands I have heard. Yes, on Jazz, it surpasses the NAD.
