Yeeeeaaaaahhhhh... I'm in the same boat, dude. I'm fairly satisfied with my Fiio E17 as a portable amp solution realizing that you're still using the iphone DAC section and headphone out. Not the most elegant solution but can improve the IE8 a bit... IMO , not enough to make it worth carrying around. Any outboard DAC that'll be compatible with lightning is gonna cost, it's just a sad truth.
I keep plugging it like I work for the company but I highly recommend the CanOpener app for Idevices. Great EQ, a setting for the IE8 is a preset, I believe and a good crossfeed program. Also offers FLAC playback and upconverting , which... not sure how that works since , I believe, the iphone only outputs 16/44 . Whatever, it's a cool app and will likely help you get a little extra something out of your IEMs.