DOC has so many differently sounding mods that it is not quite clear what you mean, of course it all really depends on your sound preferences and your earphones.
Still if you prefer the 1.2.8 as more detailed compared to DOC2008 mods I highly suggest that you try Sound Unlocked 1.2.1 by Dmitry https://yadi.sk/d/Z4Xg0f7BWJUxJ
It should be flashed as any usual update.
Also given your preference DX50 MEGA SOUND EXPLOSION SECOND EDITION by DOC would be good for you I guess https://mega.co.nz/#!T0QnCaCR!W5baLFm7SdaPFbMweKImFl_gG5zOq73JaKup289IKxU
Give us some feedback once you try these two - I hope you like them!
I just received my DX50 in the mail today, which I purchased from another Head-Fi member. I played around with firmware v1.2.8, which sounded pretty good to me, but I didn't really have anything to compare it to. I was planning to upgrade to v1.5.0 from the iBasso site, but their site is down. I guess someone forgot to pay their bill. In any case, I decided to give Sound Unlocked v1.2.1 a try based on comments from other owners on a Russian forum, and your suggestion. I found the sound and detail was similar to v1.2.8, which I liked, and it has just the right amount of bass. I'm using ATH-M50x cans with it.
I'll do more testing after my Q701s arrive in the mail, but so far I like what I hear.