Though I am much more comfortable with the ArcSaber Delta, the NanoSpeed Sigma is pretty good racket for power players. This racket in my opinion should be categorized in the Armortec line. Very solid and excellen control racket. However, it is not as easy to maneuver as the ArcSaber Delta.
I got a lot of power smashing with the Sigma (w/NBG-95 @ 24 lbs) compared to my Arc Delta (same string and tension). The Delta gave me more faster reaction and control. Not bad... but just not my cup of tea. Maybe once I am stronger I will use this racket.