What kind of temps are you running right now? If you don't know download "Hardware Monitor", its free and give you all the info you need from temperatures to fan speeds.
If you don't have a fan on the front of your case drawing air in i would suggest getting one. With that your processor is fast enough for modern gaming (I would overclock it closer to 3.0GHz though) and your power supply will need an upgrade if you go with a graphics card. 220W will not be enough with that configuration.
4xxx series ATI cards run hotter then the new 5xxx series or even 6xxx series so if heat is in question i would go with a newer card. These cards also offer entry level price and performance if that is an issue for you.
Unfortunately for a low profile card you have to pay a little bit more for it, these would be good option for you,http://www.newegg.ca/Product/Product.aspx?Item=N82E16814187126http://www.newegg.ca/Product/Product.aspx?Item=N82E16814131363
- this one will save on power and heat!
For power supply i would go with at least 450W with a graphics card, personally i don't like to have just the bare minimum wattage to run my system.
Hope this helps!