RAM Upgrade help

[rasheyz]

Hi,
I have ASUS P8P67 PRO B3 with Intel Core i5 2500K and HD 6850 Crossfire. i bought 2 x 2GB RAM G-Skill
[RipjawsX ] F3-17000CL9D-4GBXL product page http://www.gskill.com/products.php?index=366
and these r filling 2 ram slots A2 & B2.
now i am looking for ram upgrade, i want to add 2 more same ram sticks to slots A1 & B1. although i can buy these easily at
http://www.amazon.co.uk/dp/B004JPMEWE/ref=asc_df_B004JPMEWE3594768?smid=A3P5ROKL5A1OLE&tag=googlecouk06-21&linkCode=asn&creative=22206&creativeASIN=B004JPMEWE

i want to ask that will these work fine with my existing ram, someone told me it can be a compatibility issue even they are from same brand and same specifications. he advised me to sell old and buy 2 x 4gb instead.
plz help.
regards

 

[RetiredChief]

Gigabyte P55 MB.
Bought 4 Kits (2 per kit) modules over the course of a year. all were Ripjaw DDR3 -1600 @ 1.6 V. The 2 kits 2 x 2 were listed as Cl 7,7,7, the 2 Kits (2 x 4) were listed as Cl 7,8,7.
I went from 2 x 2 -> 4 x 2 -> 2 x 4 -> 4 x 4. DID NOT intermix kits - kept matched pairs together. All above combinations were stable (Used Prime 95 to test). When using the CL 7,8,7 with the CL 7,7,7 - I used the 7,8,7 in the Primary slots., Maybe I was lucky.