Hi, unless desk space is at an absolute premium, I don’t recommend either the AK or MB card over the Modius, personally. I think you’re better off either buying the Modius to pair with A3 or the Modi DAC with a MB upgrade in it. Having a separate dac and amp gives you added system flexibility (easier upgrade paths, multiple digital inputs) as a general rule. In the case of the Schiit dac modules though they have a weird quirk where they output a signal to the amp that is at a lower voltage than what a separate dac would give you, limiting the total output the amp section can provide.
IMO the Asgard 3 is the suprior amp to the Magnius overall. But, especially if you are interested in the DT1990, get the Asgard. The Magnius SE output does not perform as well at its balanced output and the DT1990 is SE only unless you mod it.
I’ve written at length about <$200 amps here: