The only reshelling service for the IE8/IE80 is Unique Melody, who upgrades the two drivers to three drivers. When I asked UM Global and Stephen Guo (UM North America), they both agree that the Merlins are a better option than the IE8x3. From people I've heard who own both, they all prefer the Merlins over the IE8x3.
Here are the two emails:
If that's the case, I'm not too surprised with the answer them as UM makes excellent CIEMs. I guess it all depends on which drivers you use and if there is good synergy between the drivers. I find 3 drivers more than enough for my set, but I want more bass extension so I'm thinking of replacing my bass driver with the Miracle's Dual Low driver.