Ps Audio BHK Signature vs Parasound Halo A 21+

MOSFET amplifiers can be very capable of providing adequate current.  The Audio by Van Alstine FET Valve 600R I have drives my Magneplanar 3.7i's very well.  Certainly as well as my Parasound Halo A21 from the listening perspective.  According to its specifications, the BHK doubles its 8 ohm output into 4 ohms.  Don't know how that can be done without increasing current commensurately.  But I'm certainly willing to be educated.