pretty quick question about ram buying

so i bought a decent rig about a a year and a half ago, maybe more, and this is what it has:

-Asus p6X58D-E -intel core i7 930 @2.8GHz -Nvidia Geforce GTX 470 -CORSAIR DOMINATOR 3GB (3 x 1GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Triple Channel Kit Desktop Memory Model TR3X3G1600C8D

so ive been playing bf3 for a while now and seems like my ram is just not enough, after playing for like 30 minutes it starts to stutter a lot wich results in me being killed so i figured its a ram problem since the ram-meter hits 90% when i play bf3. so basically what i want to do is get some more ram, ive read that its quite hard to make 2 different kinds of ram match and work properly together, so im buying ram with basically the same specs as my current one. after looking for something matchable ive come up with 2 different models, i want to keep using corsair to avoid compatibility issues.

My current ram: [1] Newegg.com - CORSAIR DOMINATOR 3GB (3 x 1GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Triple Channel Kit Desktop Memory Model TR3X3G1600C8D

-option 1: [2] Newegg.com - CORSAIR DOMINATOR 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMP6GX3M3A1600C8

-option 2 [3] Newegg.com - CORSAIR XMS3 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model TR3X6G1600C8 G

those options seem like the same to me i just dont know why the price diference but since i already use dominator series i'd like to know if it would be better to expend 20 more dollars.

thx in advance

 

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I think the GTX 470 should be able to handle it - it sit pretty high up on the charts. I would suspect the 3Gb of RAM may be a problem and bumping it up to 6Gb would make a big difference in overall computer performance. However, you did not state what OS you have. When using more than 4Gb of RAM, you MUST use a 64-bit OS.