magnepan mmgs-buy zero autoformers or stands 1st?

More current will make more of a differnce than either. 40 watts is not enough to allow them to open up and show their best.

Both are excellent ideas to try in your situation. I would suggest first checking with Paul Speltz about the Autoformers. He used to offer a 30 day guarantee, but I don't know if he still does. If he does, that would be the most practical route. If the autoformer doesn't help to your satisfaction, you've haven't lost much on the investment. In the past, I did use both the Autoformers and the Mye stands and both can tighten up the bass significantly. It could be that your tube amps damping factor is too low to get good bass and the autoformers allowing you to use the 8 ohm tap should help.

the autoformers will tighten the bass and your amps will have more effective power too. They are fun to play with, you can change the impedance of the speakers to alter the sound. I settled around 13 OHMs and that is the most popular choice according to Speltz's website. They can replace speaker wire if your run is not too long. They would be my choice - but I never heard the Mye stands when I owned my Maggie 1.6s.