You can use as many sound cards as you want, the question is whether and for what you need 2 or more.

Of course this is possible, but it makes little sense. The Soundblaster Z, for example, already has a built-in headphone amplifier for up to 600 ohms.

However, I see where you are coming from. If you combine two separate types of products (external sound card and headphone amplifier) you can achieve better results than with a combi-solution, but we are talking about combi-solutions here and therefore it would simply be a waste of money. In my eyes.