SST Son Of Ampzilla II vs Parasound A21 or A23+

A21 is a great amp IMO. Not heard the others but depending on your speakers the a23+ would probably be on the bottom of the list. 

Have you actually heard the 23+? 

I have no faith in the 21+ yet the 23+ seems like a nice upgrade on paper.

Buy this.  It’s as good or better than any of the others, but if you get the itch you can send it to SMcAudio and have them upgrade it into a truly SOTA amp for a very reasonable cost. 

https://www.ebay.com/itm/126242608801

Best of luck.

@soix thank you.  i need balanced ins. A21, A23+ or SOA II