Jurkenas

Regarding "hiss" ( white or pink noise ), it's easy to determine which amplifier is quieter. Simply put a short across whatever input (I.E. line, aux, tape, etc"). Actually solder a short across a pair of RCA pin plugs, plug them into the input under test and crank up the volume. Listen (or use a scope to measure). Any additional "hiss" that may present when driven from your iPod or any other source is in the source equipment, or in the program matter. My crystal ball says you'll find both the Dennon and the 9090 will present no appreciable "hiss" under the above test conditions using the line input (aux, tape, etc). I tend to agree the 9090 is a “better” amplifier in a general way. The 9090 was around long before the Dennon. Chances are it will be around long after the Dennon goes up in smoke. Other things .... You mention both amps have roughly the same specs. Published specs ? or actual specs ? 20 - 20,000. My 9090 is down only -2.5 DB at about 25 Khz. My point is I think you'll find the “hiss” issue stems from the source.