What's a good headphone amp for an iMac?

I need a headphone amplifier to drive my akg q701's better than the audio out on my 2011 21.5 inch iMac does. I have been looking at a couple of headphone amp's that are at a reasonable price. I've been looking at the fiioi e9, the nuforce icon 2, and the apogee one (even though it's more of a dac than an amp). I really like the apogee because of it's design and because it's made specifically for the mac, even though it's not made to be a headphone amp, I was reading about it and many people said that it's pretty decent to use as an amp. I like the e9 because I was going to get the e17 later (if i get the e9 of course) to use as a portable amp, and I like the icon 2 (even though it's over my budget) because of the design and because of the performance. Even though it's crazy expensive, I also really like the apogee duet 2 but I would rather not spend $500 for a headphone amp when I'm not even an audiophile. Which one is the best for a mac and for the akg q701's (also I will use it to get better quality out of my bose companion 20's)?