Video Card, CPU upgrade questions

Hello all. Sure you get tons of these types of posts, but here's another. My brother just picked up a desktop for me that his office was getting rid of. I cant believe what people are throwing out these days! Its got an Intel E2200 dual core processor, 2 gigs of ram, and a 150 gig HD. Even has a nice looking cooler master case. I just installed WIN XP home edition since they wiped the HD before getting rid of it.

Although this is already a big step up from my existing system, since I got it for free, I am feeling like putting some money into it. I also have aspirations of buying BF3 to play on it, although just being able to play BF2 on higher graphics settings would be nice. In general though I dont game all that much. My previous computer lasted me 8 years and it would be nice to build this into a computer that will be reliable and not terribly outdated for at least 5 years (obviously not including gaming).

My first upgrades for any computer are usually RAM followed by a video card. I am thinking I will up the RAM to 4 gigs (the max the mobo will support). I am not sure what video card I want. There are so many out there and I've never really followed them that closely. My previous computer was limited to AGP, but this computer has a PCI Express x16 slot, which I expect will significantly expand my options. Can anyone recommend a solid budget ($50-75) card that will get me humming?

The motherboard is intel model DG31PR. When I go on intel's website, it gives a whole slew of processors that are compatible with it, including quad core models. Are these really just plug and play? It looks like the only thing I might have to upgrade is the BIOS.

I will probably just upgrade the RAM and video card first, and maybe add a larger hard drive. If I find myself wishing for more speed, I'll upgrade the processor. All the quad core processors are over $100 on ebay anyway, so maybe if I wait a year or two they will come down. Aside from my questions about video cards and CPU, is there anything else I should be keeping in mind? I have been out of the computer building game for awhile.

Thanks for your help.