I have an NAD T762 receiver and I am looking at my next upgrade. I am planning on the next step being a separate amp. Then I will go to full separates. When I get the amp I am planning on going with a pre-pro of the same brand. I have heard that both of these brands have a "warm" sound. I like my receiver's sound but if I went with a separate amp would a B&K amp sound that much better than NAD amp? Has anyone compared the two?