Extra memory & other component compatibility..?

[miseryguts]

I'm planning to buy a new cooler (Noctua NH-D14) and some extra memory soon
I currently have 6Gb of Corsair CM3X2G1600C9 installed on a Gigabyte X58A-UD3R but can't seem to find the exact same modules anywhere, could people suggest some alternatives that won't present any compatibility issues or compromise the available space that the new cooler is going to occupy..?

A few further questions if I may, how much more ram is actually useful before it just starts to get a bit silly.. I do a fair amount of gaming & quite a lot of Photoshop/Premiere Pro & sound editing and was looking at adding an extra 2x 2Gb is this adequate.. too much, too little.. and does it as others have suggested reset your overclock & potentially make your processor (i7 920) a little unstable..?

Thanks.

 

[Ciff1]

x58 boards are triple channel so you really want another 3 stick kit, photoshop doesn't really use more than 6gb i have read. Anymore than 12gb and overclocking becomes difficult, also remember win 7 has ran limits 16gb for home prim, professional and ultimate 192gb. Look for ram with same timings and voltage and you should be ok to mix. Kingston hyperx genesis kit has low heat spreaders as i have a set.