I really only need something to boost the treble, so nothing fancy. The best devices I could find were the more expensive FiiO amps. Are there any other options?

I would like to get some headphones that emphasize bass, but since I can't demo any of them, I am trying to make a decision based on recommendations, reviews, and graphs. So here's the confusing part.. I'm looking through the graphs for recommendations, particularly the Beyerdynamic Custom One...