You just need an amp and a DAC or a combo amp/DAC (all-in-one amp w/ DAC built in). You shouldn't need a separate pre-amp to drive the 58X whatsoever. The idea is to make sure you can drive the headphones properly. Basically, this means that your getting a satisfying amount of volume out of them without needing to turn the volume dial all the way up (if you need to do that, then you're not getting enough power). The 58X should not need anything fancy/expensive (relatively) to drive them/make them sound good.

Edit: since you already have a FiiO K1 DAC, and the Suca Audio looks like a tube amp, that should be more than sufficient. Are you saying you're not satisfied with the amount of volume the Suca amp provides?

Edit 2: Is that Suca a pre amp? You should be using a regular amp instead of just a pre amp I believe.

Edit 3: The more I look at the Suca amp, the more I want to suggest investing in something that will provide a better, more effective listening experience. Again, you don't have to spend a lot of money to do this, but a $50 mini tube amp probably isn't going to provide you with the best that the 58X can offer. From the reviews on Amazon, people are saying that it lacks a ton of detail. Maybe look at Topping, SMSL, JDL Labs, Schiit, etc. for something that will allow your headphones to display the amount of detail and volume they're capable of. There are plenty of amps from those companies that are in the $100-$200 range.