Yep, everything is relative. With your previous 124 you had some fantastic power. Building out your stock 2020 M8 will take a bit to get it to where you want. Going with the SE Stage 3 will almost assuredly leave you disappointed still.
If it were me, I would go with the following 3 things. I believe they will get you to where you were, and beyond (if you want), be less expensive and much happier in the long run.
1. Get a good foundation with a True Stage I, plus cooling benefits (which produce more power and better reliability). Check out this
LINK to see what I'm talking about. (A AN BS is not the way to go, it will only have to be modified or it will hold back performance and create tune instability)
2. I would contact Fuel Moto. Here's their
LINK. Talk to Jamie, tell him what you have, that Kevin at DK Custom referred you, and that you are on Trike Talk Forum. They have many different levels of kits that will get you the power you are accustomed to. Much better bang for your buck than the screamin seagull stuff.
3. If the warranty is important to you, contact Jim Palmer at this
LINK. He has a warranty program that can take the place of the Factory warranty on new bikes. It far exceeds the ridiculous Limited warranty that HD has been serving up since 2017.
Interested to see how it all turns out for you, regardless what direction you go.
Kevin