Out of your list: R9 270X
What about a GTX 760? or GTX 480?
If you want to stay with AMD, then a R9 270 or HD 7870, but they are rated slightly lower than the two nvidea cards respectively.
If running the settings at high, does not play well, you can always lower them. You can always save the game, change the setting, and reload if you are having issues late game. I am not saying you need expensive memory. It was more along the lines of needing 4 GB of cheap GPU RAMM or staying with 2 GB of higher priced GPU RAMM. There is another thread about the topic. If you are going to use a couple of 40" monitors, then you are going to need more RAMM. If you are going with a 22" monitor then 2GB will be faster for you.
The issue with high end cards is coding and how to use the extra power, not that they are bad cards. Driver issues also. If you are going to play at lower settings why spend extra money, unless you have future needs for such cards?