Two questions :)
Will they sound better then the M50's with the sound card?
What's the least expensive way to "do them justice"?
Edit: I am justifying the expense by expecting these to be my headphones for the next 10-20 years, so even if my current setup does not do them justice, it's good to know I have the headroom in my headphones to do whatever the next equipment I buy justice :)
First, replying to the replyier :) - I would say that the Essence ST(X) DAC section is good enough, but the amplifier section is not good enough for most planar headphones. So, you would need an amplifier. (The new Schiit Vali was released today ($119), but no one (such as I) has received a production model, so you ought to wait a few days for a Vali-with-Alpha-Dog review to appear.)
Second, I am not buying your concept " If I am going to buy my first car, then I should just get a $200,000 Ferrari right from the beginning. " I'm sure your camera store guys were not interested in arguing against your purchase, however.
So third, in reality the Alpha Dog is a headphone for two types of people - audiophiles and musicians. In other words, people who have spent thousands of hours listening critically to the very small details of the sound of music. People who pay more than $300 for headphones are generally disappointed, because the differences are tiny subtleties that require training to hear. And please note that is not a superiority/inferiority thing (I hate the term "golden ears"), it is just what one is trained to do.
Lindsay Vonn can tell the difference between two slightly differently waxed pair of skis that I could never tell apart if I spent the whole day trying them - because she spends thousands of hours skiing.
So no, I don't recommend high-end audio gear for people buying entry level equipment.