Unfortunately, the card you are talking about is not the fastest
https://www.videocardbenchmark.net/gpu.php?gpu=Radeon+X1550&id=613but I guess your motherboard is still with an AGP graphics bus and you didn't have much choice!?
Anyway I'm going to give you a 'hidden' procedure to display your frame rate (FPS).
Once you have activated this display, you will be able to see how many FPS you have WITH and WITHOUT your graphic card.
If the numbers are almost the same, there is still a problem
- Open "mGalaxy\Data\Preferences.xml" with a text editor
- Locate this line: <advanced_showfps>false</advanced_showfps>
- Edit it to: <advanced_showfps>true</advanced_showfps>
- Save
From then, you will see the FPS displayed on the right top corner.
Check the speed of the Base theme and the 3D Themes WITH and WITHOUT your graphic card.
Report your finds here
PS: for your info, here are the typical FPS on a i3 CPU with an entry level GTX 750 at 1920x1080px resolution:
Base, Presenter, Presenter II, Stripe: 450 FPS
MyVintageRoom, MySnes, MyArcadeRoom: 100 FPS