Smartphone Buying Advice Needed

I've been using Windows Phone on the Focus Flash for some time now. I'd like to switch to an Android device.

I'd have to buy it unlocked and for less than $300 SIM-free. It should preferably, be upgradable to Android 4.1 without having to rely on a custom ROM.

My options: (the Nexus 4 is not available where I live, and importing it goes above the price point)

Sony Xperia P

HTC Amaze

Samsung Galaxy S Advance

Nexus S

Pantech Burst

LG Optimus L7 II

Any other additions are welcome and appreciated. Thanks :D