I don't know where you live so I thought I'd get the memory chips from both sides of the atlantic;
MicroDirect: Corsair® 2048MB TwinX XMS 3200 C2 Memory Kit (2 x 1GB)
NewEgg: CORSAIR XMS 2GB (2 x 1GB) 184-Pin DDR SDRAM Dual Channel Kit System Memory - Retail
I think Corsair is the best of the best mamory manufacturers. I think that either of these chips would do greatly improve the speed of you computer.