I can get 4gb of low profile kingston on ebay for a good deal; about 12 pounds and their stock is running out soon apparently, at the moment i have 8gb of corsair lp 1600 mhz ram. However the kingston ram is about 1066mhz, im assuming this will drag the corsair also down to 1066. So my question is, is it worth it throwing those in one time and will they work? Or its not worth the hassle? I don't really do any gaming but use sony vegas and photoshop now and again / internet browsing.
I'm not sure how much better the 12Gb would be than your existing 8, but even before considering buying it, make sure your existing 8Gb 1600 can even drop down to 1066. I use pcwizzard to look at the specs of my installed hardware, but I don't know if it's the best.