What should be my next Android phone, need some help...

I use a Nexus S running 4.1.2 (stock) on it. I am completely in love with JB and the smoothness offered by it..even on the single core Nexus S. It does show *some* lag on the Nexus S, but thats because its running JB, but I am probably being nitpicking as well :) .

The reason for me to look for a new phone is due to the power button on the NS, which is pretty much dead. Its been 2 years since I bought the NS.

I'm extremely comfortable and partial to the stock Android environment. I've gone from Stock GB -> Stock ICS -> Stock JB UI. Touchwiz, Sense and Blur UIs do not hold any great appeal for me. That said, I wouldn't mind using a custom UI skin. I would've gone for the Nexus 4 if it were available in India, but it'll be a while before it lands here.

Features that I'm looking for in the phone are:

  1. Good upgrade paths to JB and future versions
  2. Unlocked bootloader and Cyanogenmod support
  3. Battery life
  4. Good GPU/CPU

I have narrowed down my choices to a few devices:

  1. Samsung Galaxy S2 (Intl Version)
  2. LG Optimus 4X HD
  3. Xperia Ion

I would appreciate some suggestions from the community on which phone should I consider (among the list above or otherwise)