If you are running Vista I don't think 2GB is much good get 3GB DDR800 at least. Are you having a 32bit or 64 bit OS. I.ve got 64 and have 8GB. Everything runs so fast that this was posted before I finished typing it.
"Each memory slot can hold DDR2 PC2-5300, DDR2 PC2-4200, DDR2 PC2-6400,......with a maximum of 2GB per slot.*" (Btw, official specs say 1Gb per slot click here)
I'd go for the G.Skill modules (the ones in your basket), as they're good but not overly expensive. First check in the BIOS if you can manually increase the RAM voltage - it needs to be 1.9v to run in dual-channel mode according to one reviewer. Crucial's 2x1Gb PC2-6400 kit for the same money would be OK too, & without changing anything in the BIOS.
As the motherboard has 4 slots you could retain your old memory & have 3Gb in total if you like (Ideally you'll want to place the larger modules in Dimm slots 1 & 2). All the RAM will work at the speed of the slowest modules, but 3Gb of slightly slower RAM may well be better than 2Gb of the faster variety. G