Only about 3 pages through this thread, but wanted to express my appreciation for the issues discussed here. My situation is nearly identical to Chuck's - decent shape, 56, severe stenosis but mostly non-symptomatic, even down to concerns about having to give up Muay Thai. Came here to ask about the decision to put the surgery off or pull the trigger and have found an incredibly worthwhile discussion. Many thanks, and congrats on what's sounding like a good recovery. Now back to the thread.
Welcome to the forum Michael.
You face the two big decisions that I faced, now that you have the severe diagnosis:
1. Get AVR surgery now or wait for symptoms.
2. Mechanical or tissue valve
Like most of us here, I thought a lot about these decisions and studied a lot of published scientific literature. I also found a wealth of information and support on this forum- it is truly amazing.
At the end of the day, these decisions are an individual choice.
For me, as to wait for symptoms or get surgery, I was heavily influenced by the following:
1) The published studies which show significantly better long term outcomes if surgery is done before symptoms.
2) Feedback from this forum, suggesting that I get the surgery now while I am in good physical health.
While my cardiologist emphasized that either course was reasonable my surgeon felt strongly that I should get the surgery now and not wait. He had two very good points 1) My severity has progressed quickly in the past 6 months and 2) Sometimes the first symptom is sudden death. That one is hard to argue with.
Here is one of the studies that influenced me. It found that mortality after two years was more than twice as high for those with severe aortic stenosis who took the wait and watch approach, compared to those who had surgery before symptoms.
" The researchers found that two years after the recommended approach, survival in the AVR group was 92.5 percent compared to 83.9 percent in the WW group. "
https://www.sciencedaily.com/releases/2019/03/190326122152.htm
It should be pointed out that there is likely a difference between individuals who get surgery immediately after symptoms and those who wait a long time after they have symptoms. If one gets the surgery soon after symptoms, there is a greater chance than any structural damage can be reversed- the longer one waits after the onset of symptoms, the greater the chance of irreversible structural damage.
Here is another study that had an influence on my decision, better surgical outcome and lower mortality during the follow up period:
" In conclusion, in this randomized trial, early surgical aortic-valve replacement resulted in a significantly lower risk of operative mortality or death from cardiovascular causes during the follow-up period than conservative care among asymptomatic patients with very severe aortic stenosis. "
https://www.nejm.org/doi/full/10.1056/NEJMoa1912846
even down to concerns about having to give up Muay Thai
This was what really made it hard for me as well. At the time of surgery, I was on the MMA team at Dan Henderson's. Since you are into Muay Thai I'm guessing you may have heard of us. I spared on a weekly basis with guys like Sam Alvey and other MMA pros and amateur fighters. At the time, the Muay Thai boxing was the sport which I enjoyed the most. Going with mechanical would mean giving up sparring, with the exception of very light sparring. This was not easy for me, but ultimately I did not want to face multiple future surgeries, just so that I could keep boxing. And, the literature was pretty convincing that there is a longer life expectancy for those in our age range who choose mechanical. I really do understand why someone in their 50s would choose tissue valve. After I was diagnosed with aortic stenosis, for the next 18 months, my plan was to go tissue valve when the time came. But the more I delved into the literature and researched the subject, the more convinced I became that for someone at my age 53, mechanical would give me the best chance at a normal life expectancy.
But, these choices are yours and yours alone. There are some individuals who are in their 50s, whom I believe should choose tissue. Many variables come into play and there is no absolute right or wrong choice.
Please feel free to reach out with any questions that you may have, either here on this thread or you can private message me if you are more comfortable with that.
But in general I have energy and feel great. Not climbing any mountains, however! I'm also about 20+ years older than you are! 
Congrats on the progress.
