As said before PCI can never give you the AGP performance and if you are a gamer, there is a high chance you will be disappointed playing the latest games. I would recommend to change your mobo with a AGP card, and if you can't do it now, to make an investment plan to do it in the future. (Mobo + AGP Video + Other Core stuff).
If you spend money in a PCI, there is a possibility that it might end up as a useless card once you upgrade your PC.
Stone walls do not a prison make,
Nor iron bars a cage;
Minds innocent and quiet take
That for an hermitage;
If I have freedom in my love,
And in my soul am free,
Angels alone that soar above
Enjoy such liberty. - Richard Lovelace