Might be too late here but I have owned a Stratos and the A21. There are many Odyssey fans out there, but the A21 is just alot better. The designer, John Curl, has made a superior amp in my opinion. I had many problems with three pieces I had from Odyssey. I had a Tempest preamp, a Candela preamp and a Stratos amp with red board. All had developed hum problems and with the Stratos and Candela a spurious noise that came and went from one channel. Many, many months went by and Klaus was very difficult to get ahold of to fix these issues. I ended up selling the stuff back to him at a big loss in $$$. Just digging through the posts on audiocircle.com (the Odyssey forum) will reveal these issues.
Even without the noise issues, the A21 was much better. This amp produces music effortlessly, without any strain. It was even better than the McCormack DNA-125 that I also owned for about a year.