I'm discounting the 17" just due to the size X-D
Here's a
nice review of the A8-3500M that has both synthetic and real-world tests (be sure to look at the A8-3500M with discreet 6630M, as that is close to what the one you're looking at has). Several pages, but I know Just Cause 2 can really kill a lower-end system. Check out StarCraft 2 and other games as comparisons to what you'd be playing at. Just note that all of the systems, excluding the 17" one, have a max resolution of 1366x768, so the 1600x900 and higher resolution benchmarks are moot for you.
One major thing that would tip me toward many of the other options is that they offer Optimus (need Intel+Nvidia for this) technology, allowing the laptop to switch between integrated and dedicated graphics on the fly. This would save battery, but allow you to have better performance when you needed it.
Looking like the first Acer with the 5470 is a bit weak on the GPU side.
310M on the Samsung is also a bit weak.
The 520M on #4 is pretty decent, able to play quite of current games a bit at decent settings.
The 330M on the Acer with the touch screen is quite nice as well, somewhere near the 520M in terms of performance.
Given all of the options, you'd probably be limited by the GPU power you've got in the system, rather than CPU. That being said, I'd have to recommend either #4 #5 or #6. All of these would do quite well gaming (at least according to their benchmarks of games that are currently released). I'm not sure if the AMD A8 will use an Optimus-esque technology to switch between the integrated graphics on the chip and the dedicated 6650m that it has, but if it did it'd be hard to say no.
Given the choices of 4, 5, 6, you could compare the features to see which one fits your needs the best. But they're all pretty similar, minus the touch screen on #6. On a laptop, I don't know how much that'd be used, except perhaps with Windows 8 if you plan on upgrading.
