I do have shure 535ltd and also ak100. If u like shure 535ltd soundsig then pairing with ak100 will be fine. Ak100 does not boost the highs/mids/lows. It just follows the character of your iems or cans but with a bit of refinement to its sound. I dont think adding external amps will improve shure 535ltd sq. For me...i like to use ak100 and shure 535ltd alone rather than adding external amp. But if i use my sm64 iems...with additional amps it does improve the sound a lot. Shure 535ltd is very sensitive iems. U dont need extra power to get its maximum performance. Ak100 alone is enough imo. Just to note...sm64 is much more capable of responding to amplification compared to shure 535LTD.
Thanks a lot for your reply!