Solution
CL makes little to no difference in games and usually has a huge increase in price. But you will preferably want to get 1.5v.

I would suggest you make a thread in the systems-new build section so we could help you pick parts and stay organized in one place.
I will get this F3-12800CL8D-8GBXM, http://www.gskill.com/products.php?index=356&c1=1&c2=3, if you only like gskill.

after you read this http://www.tomshardware.co.uk/corsair-vengeance-crucial-ballistix-kingston-hyperX,review-32168.html, you know why i take that memory.

 
CL makes little to no difference in games and usually has a huge increase in price. But you will preferably want to get 1.5v.

I would suggest you make a thread in the systems-new build section so we could help you pick parts and stay organized in one place.
 
Solution
After the fact, but helpful.

Great article -> http://www.bit-tech.net/hardware/memory/2011/01/11/the-best-memory-for-sandy-bridge/1 ; ultra low CAS has it's place for multitasking intensive environments.

This are may favorite set for the LGA 1155; F3-12800CL8D-8GBXM http://www.newegg.com/Product/Product.aspx?Item=N82E16820231445 you do want at least 8GB for gaming especially with 64-bit games; see -> http://www.tomshardware.com/reviews/ram-memory-upgrade,2778-8.html

BTW - don't forget to purchase a 64-bit OS ;)
 
The answer, like in may things computing is, it depends....typically we will see only a 2-5 % performance increase in average fps.....but the increase in total system cost is less than that, then it is kind of hard to argue against the investment. In a addition usually where ya see an impact, it's on min fps more than average.

In the above link, we see a 4.5% increase in min fps and that will come at an extra cost of $44 for 8GB. On a $2k box, that's a 2% increase in cost or about a 2 to 1 return on investment. Some would argue that you won't notice the difference, then again if ya spending $2k, ya ain't likely to notice the $44 :)

Here's a other investigation where the results were a bit more dramatic

http://www.anandtech.com/show/2792/12

22.3 % (SLI) increase in minimum frame rates w/ C6 instead of C8 in Far Cry 2
18% (single card) / 5% (SLI) increase in minimum frame rates w/ C6 instead of C8 in Dawn of War
15% (single card) / 5% (SLI) increase in minimum frame rates w/ C6 instead of C8 in World in Conflict

Here's what I am currently putting (All DDR3-1600) in my builds:

$50 CAS 9 Corsair Low Profile Vengeance 2 x 4GB
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233196

$65 CAS 8 Corsair Low Profile Vengeance 2 x 4GB
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233199

$95 Mushkin Low Profile Raddioactive or Redline
http://www.newegg.com/Product/Product.aspx?Item=N82E16820226221
http://www.newegg.com/Product/Product.aspx?Item=N82E16820226178
 
I keep seeing your post http://www.anandtech.com/show/2792/12 and assume it translates to ALL MOBO's, but it doesn't with the LGA 1155. The 'fixed' BCLK and to a degree the SB IMC of the LGA 1155 has more like a wall with DDR3-1600 CAS 8/9. On anything else that allows BCLK/FSB adjustment i.e. higher settings then sure you get the additional FPS above a ±1~±2 which is within the margin of error.

Thomas's review showed the same results -> http://www.tomshardware.com/reviews/corsair-vengeance-crucial-ballistix-kingston-hyperX,2907-8.html

'Hopefully' this will change with the SB-E / LGA 2011 with an adjustable BCLK.