[mrconfuse]

I own the Ak100 and I use it with the Shure 425. I don't particularly like the sound that the pairing produces. And I ended up using my phone (note 4) for a while with the 425 but i want more. So I started looking at external Dac/amps (priced between $200 - $300) but it occurred to me that for a little more I can move back to the Ak100 if get a different IEM. I'm thinking about the Westone UM Pro 30 or the Etymotic ER-4PT. 
 
So now what do I do? Get a new set of IEM or DAC for the note 4? For the DAC i narrowed it to the Apogee groove/Centrance Dacport HD/ 

 

[Signo]

I would go for the Westone Pro 30 as they have lots of good reviews and new set of IEM or headphones really do make a big difference.  Then save your cash for the Centrance.
 
Note:- I was in your same boat about 6 months ago and I got the Shure 535 first then Fiio E12A.  The combo is very good, but I found the most impact came from the IEM.