Originally Posted by theberkin8or
So does that mean a DAC is my bottle neck on SQ?
It could be the DAC, depending on what you're using, but it also could be the music files (poor mastering), your ears, or the headphones. In general after a certain point, you're better off finding better music than better gear (gear that's not new headphones); once you have a reasonable DAC and a headphone amp to your liking that can power your headphones, there's not really big improvements to be had.
Starting off the OP with "getting the most out of" X is not particularly the best way to phrase it if you'd rather not spend a lot of money. You can always do better, and you may sometimes or often do audibly better.
If for some reason you wanted to spend up to your budget limit, CEntrance DACport should be very good and fit in at $400. The integrated headphone output is slightly more powerful than the E11 so also enough.