Just curious to know what the output of the amps are into 6ohm load - my speakers (MA GS-60 6ohm) recommend an amp in the 60-200 watt power range. R9V3SE is rated at 175w 8ohm or 335 4ohm. How do I classify the output on the Nuforce on my speakers - do I need to know the amp Volts output and refer to Ohms law to calc watts at the load (watts equal voltage squared divided by impedance)
Not technically able to compute the exact wattage, but with those speakers it is of little concern. Best estimate would be around 255wpc.
Those power ratings for speakers are simply "recommended" guidelines for the impedance and efficiency of the speaker for good performance. Using a higher rating will not cause damage, unless played to a level that causes "clipping" in the amp. In general, a higher power rating will reduce the chances of clipping, and be safer with your speakers.
The same is not true for the "lower" power rating, and low power can cause clipping more easily.
You should be fine with a fully functioning Ref-9.
