I bought this RAM module :
G.SKill Ripjaws X 2x4 GB PC3-12800 DD3-1600 9-9-9-24

And I installed on this motherboard :
Gigabyte EP45C-DS3R

Normally this board is supposed to accept a maximum of 4GB of DDR3; it happens that it is possible to put 8GB on it.
The only thing I did : update the BIOS to F5 revision.
This operation can be interesting to boost an old configuration, plus, the average price of DDR2 is quite high these days...and of course DDR3 is really cheap so it's a very good deal to buy some DDR3 now (June 2013)