The R1.5 appears to be a very high bias Class A amp. Based on the overhead draw (260 watts as idle), I would guess you are looking at a Class A bias somewhere between 25 and 40 watts per channel. Please be aware that the amp will draw 55 watts constantly when power off (apparently voltage is kept active to the main power supply so that it is kept in a "warmed up" state). The amp seems to have very nice reviews on sound quality. It is a much higher Class A bias than the Parasound A21 (which I would guess is bias to about 10 watts per channel).
It's very difficult to tell from photos, but it *appears* that the Usher 6.0 uses the exact same power supply as the R1.5. It is listed as 125 watts per each of the 6 channels. This amp will NOT be biased into Class A and will run as a Class AB amp only (or it may be biased very low like a few watts). You will also have less output transistors per channel (probably about 4 transistors per channel compare to the 12-16 transistors of the R1.5).
If you did choose the Usher R1.5, I would be somewhat thoughtful about matching a preamp. I have found that when you place too many "Class A" circuits in an audio chain, the sound can start to get too warm/slow/dull and you lose the attack / impact / resolution. It's a fine line and it depends on how much "Class A" waveform smoothing a particular preamp adds to the signal.
