Without going into a lot of technical mumbo-jumbo, almost all of the "hiss/white noise" is contributed by the preamp. If the amp is the dominat contributor to the "noise floor", then take it back. It should not be.
High noise necessary for imaging?? A new level of crap from a hi-fi salesman. Ranks up there with the all-time worst.
High noise necessary for imaging?? A new level of crap from a hi-fi salesman. Ranks up there with the all-time worst.