8 GB running @ 1140 MHz -- will it bottleneck my 7970? 8 GB vs 16 GB?

[booseek]

ASUS P7P55D-E LX (one PCI-E x16 slot)
i5-750 @ 3.8 GHz
XFX 5870 1 GB
8 GB RAM @ 1140 MHz @ CAS 8 (downclocked from 1333 when overclocking CPU)
CORSAIR CMPSU-750TX
1920 x 1080 monitor @ 60 Hz, FPS capped to 60

I am looking to upgrade my 5870 probably to a 7970 soon. Due to my CPU overclock, I cannot get my RAM past 1140 MHz. I'm wondering if this will bottleneck me. Should I buy some CAS 9 2133 MHz RAM, and if it downclocks by 15% as well, just run it at ~1800 MHz?

I'm looking for value. $70 - $130 for an extra 3 FPS is definitely not worth it. Also, 8 GB or 16 GB for a gamer? I see that Crytek recommends 8 GB of RAM for Crysis 3, which seems too high, but is the recommendation, anyway. Is this a sign of things to come for other graphically-intense games or other games in general? I always like being a step beyond the recommended specifications.

 

[TenPc]

Don't overclock the CPU and you will get your ram speeds returned.

 

[booseek]

Don't overclock the CPU and you will get your ram speeds returned.

I know that. My question was whether or not the RAM at 1140 MHz would bottleneck my system if I were to get a 7970. My other question was if it is worth it to upgrade to 2133 RAM to run at ~1800 MHz given the same worst-case scenario underclock. Again, this is a question about value; a 3 FPS increase does not matter to me, but a 10 FPS increase might.