8GB 1600 OR 8GB 1866 OR 12GB 1333 OR 12GB 1600

8GBs of 1600 is good enough.

ok thanks  

I won't ague 2x4GB (8GB) Kit of DDR3-1600 IF you have an Intel SB, SB-E, IB or i7-9XX AND a Chipset that supports it.

Otherwise what CPU & MOBO?!

Z77 Gigabyte, and 2600k

That should have no problems with the 2x 4GBs 1600.

2x4GB (8GB) Kit of DDR3-1600 @ 1.50v or 1.35v from a reputable company like Corsair, Mushkin, G.SKILL, etc.

DDR3L (1.35v):
G.SKILL F3-12800CL9D-8GBXM
Mushkin 996988

DDR3 (1.50v):
G.SKILL F3-12800CL8D-8GBXM
Mushkin 997043
Corsair LP CML8GX3M2A1600C9
Corsair CMZ8GX3M2A1600C9
Corsair CMD8GX3M2A1600C9 ; NEW & Cool

Ok thanks, how about this: http://www.scan.co.uk/products/8gb-(2x4gb)-corsair-ddr3-vengeance-jet-black-lp-pc3-12800-(1600)-non-ecc-cas-9-9-9-24-xmp-15v

ok thanks  

That should be fine, But just a couple of comments.
SB CPU defaults to 1333 (the spec), IB defaults to 1600 (the spec).
For SB using DDR3-1600 At 1600 May void the CPU warrantee when run at 1600. This will only matter if you have to RMA the CPU and then it depends on the "intel" rep that you talk to.
For What's it worth there is VERY little diff between 1333 and 1600, And I'm running DDR3-1600 @ CL7 @ 1.60 V on my I5-2500K

Also DDR3 @ 1.35 Volts is below the Min spec for SB which is 1.425 -> 1.575 V (DDR3 @ 1.5 V is the correct choice)

ok thanks  

Those are the CML8GX3M2A1600C9 I linked above (LP Low Profile) and are fine.  

It all depends on whether the CPU requires FSB Parity with the ram, then whether the ram speed is supported by the motherboard. State you PC specs and then it can be better ascertained. Usually, though, 8gb 1600 is better.

I5 2500k
Gigabyte z77 motherboard (£77)
Gtx 670

Intel® Core™ i5-2500K Processor (6M Cache, up to 3.70 GHz)
http://ark.intel.com/products/52210/Intel-Core-i5-2500K...(6M-Cache-up-to-3_70-GHz)

Max Memory Size (dependent on memory type) 32 GB
Memory Types DDR3-1066/1333
# of Memory Channels 2

http://www.gigabyte.us/products/product-page.aspx?pid=4...
GA-Z77X-D3H
Support for DDR3 2400(OC)/1600/1333/1066 MHz memory modules

It doesn't refer to FSB only that "Some Intel® Core™ processors require a graphic card, please refer "CPU support List" for more information."

The CPU only supports 2 ram modules so if you intend on 8gb then
2 x 4gb DDR3-1066/1333 (to ensure no errors) in slots 1 & 3

I'd suggest the Crucial brand rather than Corsair, personally, I think those ram sticks with those fancy heat sinks do more harm than good.

A 2500k can handle more than just 2 RAM sticks. It may be a dual channel processor, but that doesn't mean you need 2 it means you need them in sets of 2.

It could do 4x 4GBs or 4x 8GBs just fine, there is just not usually a reason to use more than 2x 4GBs for a gaming PC because games don't use a lot of RAM. For backwards compatibility they usually only use 2 GBs or less.

Crucial and Kingston, however, do have quite a bit lower rates of problems right out of the box.

OOPS! Sorry, "Each memory channel can handle up to two memory modules"
http://www.tomshardware.com/forum/292311-28-memory-chan...