Welcome to the site!
So you can upgrade the Video card to the card that you posted, but you already have 4GB of RAM and the CPU socket is AM2+, which means no Intel upgrade unless you're looking to overhaul the motherboard as well. Given what you already have, your bottleneck is the GPU anyway, so upgrading that and that alone will be sufficient. Considering that you only have two DDR2 slots, you would need to get 2x 4GB sticks for a total of 8GB, but it's really not needed (although it's not terribly expensive so if you have the budget, you certainly can consider it). What are you looking to do with the computer that you need upgrades? Basic gaming would see improvement by simply upgrading the Video card. It should be noted that you're looking to purchase a PCIe x16 2.0 card and only have a regular PCIe x16 slot. While there's not going to be any issues with compatibility, just thought you'd like to know.
For a RAM upgrade, consider the following:
Supported DIMM types:
PC2-5300 (667 MHz)
PC2-6400 (800 MHz)
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?