I own amps from 4 different manufactures:
Crown, Behringer, Adcom, Parasound. My 2.0 is a pair of Curt Campbell Statements and source
is a computer with a regulated linear DC power supply (no switch mode)and an EMU 1212M pro-audio
mastering grade sound card.
I welcome people to come over any time and compare the Parasound to my cheapie, clearance Crown XLS402d ($179)
Would I pesonally go out of my way to pick up a Parasound A21 or 2250 vs an XPA-2? Based on experience, no.
I had an XPA-3 years ago for a long weekend. It held it's own quite nicely. Then it went to a customers house.
For the cost of the A21 I would pick up two XPA-1 (fully differential, balanced back to front.