I Recently purchased the Halo A21 and A52+. Both sound wonderful. They replaced a Parasound NC 2250 and 5250 in my system. The Parasound product is very hard to beat for the money.
If if you look at the innards of both the A21 and the A21+ they appear to have very similar topology. The majors gains in the A21+ come from a much more robust Power Supply and refinement of the A21 design.
I wrote an end-user review of my impressions on the equipment if interested...
https://www.avnirvana.com/threads/a-subjective-review-of-the-parasound-a21-and-a52-amplifiers.3969/
BTW... the high end is extended and pristine with my speakers. I would guess that some speaker/amp/cable combinations may adversely affect the amps ability to deliver full range sound but would think you would have to work very hard, or be extremely unlucky to come across that negatively impactful combination :-)
If if you look at the innards of both the A21 and the A21+ they appear to have very similar topology. The majors gains in the A21+ come from a much more robust Power Supply and refinement of the A21 design.
I wrote an end-user review of my impressions on the equipment if interested...
https://www.avnirvana.com/threads/a-subjective-review-of-the-parasound-a21-and-a52-amplifiers.3969/
BTW... the high end is extended and pristine with my speakers. I would guess that some speaker/amp/cable combinations may adversely affect the amps ability to deliver full range sound but would think you would have to work very hard, or be extremely unlucky to come across that negatively impactful combination :-)