A $200 dollar budget will be huge, considering what you are starting with.
You are currently used to onboard graphics (very weak) and I imagine any dedicated graphics card will give you a HUGE boost in performance. Spending 200 on a video card and PSU to power it might only give you the same benefit as spending $50-70 on a videocard that will run off your current power configuration.
Are you gaming? Encoding Video? If you are only using the computer for surfing and media (watching/listening to video/musuic) then all of this is very academic, and you could enjoy a better experience with a very small investment.
If you plan on playing games, then your resolution is also of concern, but your whole system will be holding back your GPU. That is not to say that your computer will not play games well, it can be a fun gaming machine for sure, but again, spending 200 may not be any better than spending 50.
Not a gamer? I would suggest:
ATI
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102817&cm_re=ati_video_card-_-14-102-817-_-Product - 34.99
Nvidia
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127454&cm_re=210-_-14-127-454-_-Product - 44.99
Low power, low heat, will fulfill your needs without requiring any other upgrades like a Power supply or case ventilation.
Want to play some games with resolutions at or lower than 1650x1080?:
ATI
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127440&cm_re=4670-_-14-127-440-_-Product - 39.99 after MIR and free shipping
Nvidia
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127456&cm_re=220_video_card-_-14-127-456-_-Product - 54.99 after MIR
They both use the motherboard to power to cards and would give respectable gaming performance without needing a new PSU.
Gaming on 1920x1080 or higher resolution, and want lots of sparkly settings? You will, in all likelihood need a new Power supply to run a card strong enough to give that to your. Luckily, they don't have to be expensive to be good. But, as you get into higher power Graphics cards, you also get into higher amounts of heat to exhaust from the case. If you go this route, prepare to invest in a couple $10 case fans to help in ventilation.
PSU
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371006&cm_re=antec_PSU-_-17-371-006-_-Product - 59.99 and will power any video card you might be able to make use of in your current system.
ATI
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127435&cm_re=4850-_-14-127-435-_-Product - 104.99 after MIR
Nvidia
http://www.newegg.com/Product/Product.aspx?Item=N82E16814261050&cm_re=250_GTS-_-14-261-050-_-Product - 124.99