I'm running stock EI2 with root, so where did Ek1 come from? Some OTA that disappeared?
Although it doesn't make sense, EK1 kernel is older than EI2... my understanding is that it never shipped with any phone but was a "leak" of somekind. My suggestion is avoid it, plus you may have issues using the radios (infamous RIL issue) by changing core kernel version without the full ROM to go with it.
There has never as been an OTA or update of anykind for this device, although there are several modified kernels and a handful of ROMs, but all of which are stock-based and either heavily themed or modded. These ROMs, kernels, and a lot of active discussion can be found at RootzWiki in this forum and also by IRC in #stratosphere on irc.andirc.net, usually late evenings are best to catch the developers and testers in there.
EDIT: My mistake, I was think EH1 not EK1... the EK1 Kernel is believed to be a leak from Samsung (there is no evidence or proof of where it came from) that appeared early December 2011 and there is no kernel source available for it, and it will only work properly with this ROM or WiFi and possibly other radios will not work. It was originally leaked into the IRC channel and the author promised source, etc. and it never arrived and he has since disappeared and never returned, so the actual source of this kernel is still unknown and unverified. My suggestions would still be to avoid it, there are very good EI2 build out there by KnightCrusader, rhcp, and bag and several ROMs such as Tweaked, Ti-X, and Bones (technically still in alpha) that are stable and very usable.
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